diff --git a/app/modules/billing/routes/api/admin.py b/app/modules/billing/routes/api/admin.py
index f5735e31..203a3785 100644
--- a/app/modules/billing/routes/api/admin.py
+++ b/app/modules/billing/routes/api/admin.py
@@ -59,8 +59,17 @@ def list_subscription_tiers(
     """List all subscription tiers."""
     tiers = admin_subscription_service.get_tiers(db, include_inactive=include_inactive, platform_id=platform_id)
 
+    from app.modules.tenancy.models import Platform
+
+    platforms_map = {p.id: p.name for p in db.query(Platform).all()}
+    tiers_response = []
+    for t in tiers:
+        resp = SubscriptionTierResponse.model_validate(t)
+        resp.platform_name = platforms_map.get(t.platform_id) if t.platform_id else None
+        tiers_response.append(resp)
+
     return SubscriptionTierListResponse(
-        tiers=[SubscriptionTierResponse.model_validate(t) for t in tiers],
+        tiers=tiers_response,
         total=len(tiers),
     )
 
diff --git a/app/modules/billing/routes/api/merchant.py b/app/modules/billing/routes/api/merchant.py
index 926a396b..5ea5c7d0 100644
--- a/app/modules/billing/routes/api/merchant.py
+++ b/app/modules/billing/routes/api/merchant.py
@@ -19,6 +19,7 @@ registration under /api/v1/merchants/billing/*).
 import logging
 
 from fastapi import APIRouter, Depends, HTTPException, Path, Query, Request
+from pydantic import BaseModel
 from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_merchant_from_cookie_or_header
@@ -97,13 +98,15 @@ def list_merchant_subscriptions(
     merchant = _get_user_merchant(db, current_user)
     subscriptions = subscription_service.get_merchant_subscriptions(db, merchant.id)
 
-    return {
-        "subscriptions": [
-            MerchantSubscriptionResponse.model_validate(sub)
-            for sub in subscriptions
-        ],
-        "total": len(subscriptions),
-    }
+    items = []
+    for sub in subscriptions:
+        data = MerchantSubscriptionResponse.model_validate(sub).model_dump()
+        data["tier"] = sub.tier.code if sub.tier else None
+        data["tier_name"] = sub.tier.name if sub.tier else None
+        data["platform_name"] = sub.platform.name if sub.platform else ""
+        items.append(data)
+
+    return {"subscriptions": items, "total": len(items)}
 
 
 @router.get("/subscriptions/{platform_id}")
@@ -129,6 +132,11 @@ def get_merchant_subscription(
             detail=f"No subscription found for platform {platform_id}",
         )
 
+    sub_data = MerchantSubscriptionResponse.model_validate(subscription).model_dump()
+    sub_data["tier"] = subscription.tier.code if subscription.tier else None
+    sub_data["tier_name"] = subscription.tier.name if subscription.tier else None
+    sub_data["platform_name"] = subscription.platform.name if subscription.platform else ""
+
     tier_info = None
     if subscription.tier:
         tier = subscription.tier
@@ -142,7 +150,7 @@ def get_merchant_subscription(
         )
 
     return {
-        "subscription": MerchantSubscriptionResponse.model_validate(subscription),
+        "subscription": sub_data,
         "tier": tier_info,
     }
 
@@ -180,6 +188,40 @@ def get_available_tiers(
     }
 
 
+class ChangeTierRequest(BaseModel):
+    """Request for changing subscription tier."""
+
+    tier_code: str
+    is_annual: bool = False
+
+
+@router.post("/subscriptions/{platform_id}/change-tier")
+def change_subscription_tier(
+    request: Request,
+    tier_data: ChangeTierRequest,
+    platform_id: int = Path(..., description="Platform ID"),
+    current_user: UserContext = Depends(get_current_merchant_from_cookie_or_header),
+    db: Session = Depends(get_db),
+):
+    """
+    Change the subscription tier for a specific platform.
+
+    Handles both Stripe-connected and non-Stripe subscriptions.
+    """
+    merchant = _get_user_merchant(db, current_user)
+    result = billing_service.change_tier(
+        db, merchant.id, platform_id, tier_data.tier_code, tier_data.is_annual
+    )
+    db.commit()
+
+    logger.info(
+        f"Merchant {merchant.id} ({merchant.name}) changed tier to "
+        f"{tier_data.tier_code} on platform={platform_id}"
+    )
+
+    return result
+
+
 @router.post(
     "/subscriptions/{platform_id}/checkout",
     response_model=CheckoutResponse,
diff --git a/app/modules/billing/schemas/billing.py b/app/modules/billing/schemas/billing.py
index 1b3868a8..580c4323 100644
--- a/app/modules/billing/schemas/billing.py
+++ b/app/modules/billing/schemas/billing.py
@@ -74,6 +74,7 @@ class SubscriptionTierResponse(BaseModel):
     price_monthly_cents: int
     price_annual_cents: int | None = None
     platform_id: int | None = None
+    platform_name: str | None = None
     stripe_product_id: str | None = None
     stripe_price_monthly_id: str | None = None
     stripe_price_annual_id: str | None = None
diff --git a/app/modules/billing/services/admin_subscription_service.py b/app/modules/billing/services/admin_subscription_service.py
index 649b9b25..6a334a8e 100644
--- a/app/modules/billing/services/admin_subscription_service.py
+++ b/app/modules/billing/services/admin_subscription_service.py
@@ -204,12 +204,25 @@ class AdminSubscriptionService:
         result = self.get_subscription(db, merchant_id, platform_id)
         sub, merchant = result
 
+        # Handle tier_code separately: resolve to tier_id
+        tier_code = update_data.pop("tier_code", None)
+        if tier_code is not None:
+            if sub.stripe_subscription_id:
+                from app.modules.billing.services.billing_service import billing_service
+                billing_service.change_tier(
+                    db, merchant_id, platform_id, tier_code, sub.is_annual
+                )
+            else:
+                tier = self.get_tier_by_code(db, tier_code)
+                sub.tier_id = tier.id
+
         for field, value in update_data.items():
             setattr(sub, field, value)
 
         logger.info(
             f"Admin updated subscription for merchant {merchant_id} "
             f"on platform {platform_id}: {list(update_data.keys())}"
+            + (f", tier_code={tier_code}" if tier_code else "")
         )
 
         return sub, merchant
diff --git a/app/modules/billing/services/subscription_service.py b/app/modules/billing/services/subscription_service.py
index fe893dc0..a0d7fb76 100644
--- a/app/modules/billing/services/subscription_service.py
+++ b/app/modules/billing/services/subscription_service.py
@@ -96,7 +96,8 @@ class SubscriptionService:
             db.query(MerchantSubscription)
             .options(
                 joinedload(MerchantSubscription.tier)
-                .joinedload(SubscriptionTier.feature_limits)
+                .joinedload(SubscriptionTier.feature_limits),
+                joinedload(MerchantSubscription.platform),
             )
             .filter(
                 MerchantSubscription.merchant_id == merchant_id,
diff --git a/app/modules/billing/static/admin/js/subscription-tiers.js b/app/modules/billing/static/admin/js/subscription-tiers.js
index 46bbf4bc..66979f47 100644
--- a/app/modules/billing/static/admin/js/subscription-tiers.js
+++ b/app/modules/billing/static/admin/js/subscription-tiers.js
@@ -22,6 +22,8 @@ function adminSubscriptionTiers() {
         tiers: [],
         stats: null,
         includeInactive: false,
+        platforms: [],
+        filterPlatformId: '',
 
         // Feature management
         features: [],
@@ -51,7 +53,8 @@ function adminSubscriptionTiers() {
             stripe_product_id: '',
             stripe_price_monthly_id: '',
             is_active: true,
-            is_public: true
+            is_public: true,
+            platform_id: null
         },
 
         async init() {
@@ -67,7 +70,8 @@ function adminSubscriptionTiers() {
                 await Promise.all([
                     this.loadTiers(),
                     this.loadStats(),
-                    this.loadFeatures()
+                    this.loadFeatures(),
+                    this.loadPlatforms()
                 ]);
                 tiersLog.info('=== SUBSCRIPTION TIERS PAGE INITIALIZED ===');
             } catch (error) {
@@ -92,6 +96,7 @@ function adminSubscriptionTiers() {
                 params.append('include_inactive', this.includeInactive);
                 if (this.sortBy) params.append('sort_by', this.sortBy);
                 if (this.sortOrder) params.append('sort_order', this.sortOrder);
+                if (this.filterPlatformId) params.append('platform_id', this.filterPlatformId);
 
                 const data = await apiClient.get(`/admin/subscriptions/tiers?${params}`);
                 this.tiers = data.tiers || [];
@@ -125,6 +130,22 @@ function adminSubscriptionTiers() {
             }
         },
 
+        async loadPlatforms() {
+            try {
+                const data = await apiClient.get('/admin/platforms');
+                this.platforms = (data.platforms || []).map(p => ({ id: p.id, name: p.name }));
+                tiersLog.info(`Loaded ${this.platforms.length} platforms`);
+            } catch (error) {
+                tiersLog.error('Failed to load platforms:', error);
+            }
+        },
+
+        getPlatformName(platformId) {
+            if (!platformId) return 'Global';
+            const platform = this.platforms.find(p => p.id === platformId);
+            return platform ? platform.name : `Platform #${platformId}`;
+        },
+
         openCreateModal() {
             this.editingTier = null;
             this.formData = {
@@ -137,7 +158,8 @@ function adminSubscriptionTiers() {
                 stripe_product_id: '',
                 stripe_price_monthly_id: '',
                 is_active: true,
-                is_public: true
+                is_public: true,
+                platform_id: null
             };
             this.showModal = true;
         },
@@ -154,7 +176,8 @@ function adminSubscriptionTiers() {
                 stripe_product_id: tier.stripe_product_id || '',
                 stripe_price_monthly_id: tier.stripe_price_monthly_id || '',
                 is_active: tier.is_active,
-                is_public: tier.is_public
+                is_public: tier.is_public,
+                platform_id: tier.platform_id || null
             };
             this.showModal = true;
         },
diff --git a/app/modules/billing/templates/billing/admin/subscription-tiers.html b/app/modules/billing/templates/billing/admin/subscription-tiers.html
index 782ca10b..df4b5ab8 100644
--- a/app/modules/billing/templates/billing/admin/subscription-tiers.html
+++ b/app/modules/billing/templates/billing/admin/subscription-tiers.html
@@ -71,6 +71,13 @@
             <input type="checkbox" x-model="includeInactive" @change="loadTiers()" class="mr-2 rounded border-gray-300 dark:border-gray-600 dark:bg-gray-700">
             Show inactive tiers
         </label>
+        <select x-model="filterPlatformId" @change="loadTiers()"
+                class="px-3 py-1.5 text-sm border border-gray-300 rounded-lg dark:border-gray-600 dark:bg-gray-700 dark:text-gray-300">
+            <option value="">All Platforms</option>
+            <template x-for="p in platforms" :key="p.id">
+                <option :value="p.id" x-text="p.name"></option>
+            </template>
+        </select>
     </div>
 
     <button
@@ -87,6 +94,7 @@
     <table class="w-full whitespace-nowrap">
         {% call table_header_custom() %}
             <th class="px-4 py-3">#</th>
+            <th class="px-4 py-3">Platform</th>
             {{ th_sortable('code', 'Code', 'sortBy', 'sortOrder') }}
             {{ th_sortable('name', 'Name', 'sortBy', 'sortOrder') }}
             <th class="px-4 py-3 text-right">Monthly</th>
@@ -98,7 +106,7 @@
         <tbody class="bg-white divide-y dark:divide-gray-700 dark:bg-gray-800">
             <template x-if="loading">
                 <tr>
-                    <td colspan="8" class="px-4 py-8 text-center text-gray-500 dark:text-gray-400">
+                    <td colspan="9" class="px-4 py-8 text-center text-gray-500 dark:text-gray-400">
                         <span x-html="$icon('refresh', 'inline w-6 h-6 animate-spin mr-2')"></span>
                         Loading tiers...
                     </td>
@@ -106,7 +114,7 @@
             </template>
             <template x-if="!loading && tiers.length === 0">
                 <tr>
-                    <td colspan="8" class="px-4 py-8 text-center text-gray-500 dark:text-gray-400">
+                    <td colspan="9" class="px-4 py-8 text-center text-gray-500 dark:text-gray-400">
                         No subscription tiers found.
                     </td>
                 </tr>
@@ -114,6 +122,7 @@
             <template x-for="(tier, index) in tiers" :key="tier.id">
                 <tr class="text-gray-700 dark:text-gray-400" :class="{ 'opacity-50': !tier.is_active }">
                     <td class="px-4 py-3 text-sm" x-text="tier.display_order"></td>
+                    <td class="px-4 py-3 text-sm" x-text="tier.platform_name || 'Global'"></td>
                     <td class="px-4 py-3">
                         <span class="px-2 py-1 text-xs font-medium rounded-full"
                               :class="{
@@ -186,6 +195,21 @@
                 >
             </div>
 
+            <!-- Platform -->
+            <div>
+                <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">Platform</label>
+                <select
+                    x-model="formData.platform_id"
+                    :disabled="editingTier"
+                    class="w-full px-3 py-2 border border-gray-300 rounded-lg dark:border-gray-600 dark:bg-gray-700 dark:text-white disabled:opacity-50"
+                >
+                    <option :value="null">Global (all platforms)</option>
+                    <template x-for="p in platforms" :key="p.id">
+                        <option :value="p.id" x-text="p.name"></option>
+                    </template>
+                </select>
+            </div>
+
             <!-- Name -->
             <div>
                 <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">Name</label>
diff --git a/app/modules/billing/templates/billing/merchant/dashboard.html b/app/modules/billing/templates/billing/merchant/dashboard.html
index 28019772..da13c8f6 100644
--- a/app/modules/billing/templates/billing/merchant/dashboard.html
+++ b/app/modules/billing/templates/billing/merchant/dashboard.html
@@ -77,7 +77,7 @@
                 <template x-for="sub in subscriptions" :key="sub.id">
                     <div class="flex items-center justify-between p-4 border border-gray-100 rounded-lg hover:bg-gray-50 transition-colors">
                         <div>
-                            <p class="font-semibold text-gray-900" x-text="sub.platform_name || sub.store_name || 'Subscription'"></p>
+                            <p class="font-semibold text-gray-900" x-text="sub.platform_name || 'Subscription'"></p>
                             <p class="text-sm text-gray-500">
                                 <span x-text="sub.tier" class="capitalize"></span> &middot;
                                 Renews <span x-text="formatDate(sub.period_end)"></span>
diff --git a/app/modules/billing/templates/billing/merchant/subscription-detail.html b/app/modules/billing/templates/billing/merchant/subscription-detail.html
index 3f6a9be8..0ffd9893 100644
--- a/app/modules/billing/templates/billing/merchant/subscription-detail.html
+++ b/app/modules/billing/templates/billing/merchant/subscription-detail.html
@@ -42,7 +42,7 @@
         <!-- Main Details Card -->
         <div class="bg-white rounded-lg shadow-sm border border-gray-200">
             <div class="px-6 py-4 border-b border-gray-200 flex items-center justify-between">
-                <h3 class="text-lg font-semibold text-gray-900" x-text="subscription?.platform_name || subscription?.store_name || 'Subscription'"></h3>
+                <h3 class="text-lg font-semibold text-gray-900" x-text="subscription?.platform_name || 'Subscription'"></h3>
                 <span class="px-3 py-1 text-sm font-semibold rounded-full"
                       :class="{
                           'bg-green-100 text-green-800': subscription?.status === 'active',
@@ -68,8 +68,8 @@
                         <dd class="mt-1 text-lg font-semibold text-gray-900" x-text="formatDate(subscription?.period_end)"></dd>
                     </div>
                     <div>
-                        <dt class="text-sm font-medium text-gray-500">Store Code</dt>
-                        <dd class="mt-1 text-sm font-mono text-gray-700" x-text="subscription?.store_code || '-'"></dd>
+                        <dt class="text-sm font-medium text-gray-500">Platform</dt>
+                        <dd class="mt-1 text-sm text-gray-700" x-text="subscription?.platform_name || '-'"></dd>
                     </div>
                     <div>
                         <dt class="text-sm font-medium text-gray-500">Created</dt>
@@ -105,16 +105,32 @@
             </div>
         </div>
 
-        <!-- Upgrade Action -->
-        <div class="flex justify-end" x-show="subscription?.status === 'active' || subscription?.status === 'trial'">
-            <button @click="requestUpgrade()"
-                    :disabled="upgrading"
-                    class="inline-flex items-center px-5 py-2.5 text-sm font-semibold text-white bg-indigo-600 rounded-lg hover:bg-indigo-700 transition-colors disabled:opacity-50">
-                <svg class="w-4 h-4 mr-2" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M5 10l7-7m0 0l7 7m-7-7v18"/>
-                </svg>
-                <span x-text="upgrading ? 'Processing...' : 'Upgrade Plan'"></span>
-            </button>
+        <!-- Change Plan -->
+        <div x-show="availableTiers.length > 0 && (subscription?.status === 'active' || subscription?.status === 'trial')"
+             class="bg-white rounded-lg shadow-sm border border-gray-200">
+            <div class="px-6 py-4 border-b border-gray-200">
+                <h3 class="text-lg font-semibold text-gray-900">Change Plan</h3>
+            </div>
+            <div class="p-6 grid grid-cols-1 sm:grid-cols-3 gap-4">
+                <template x-for="t in availableTiers" :key="t.code">
+                    <div class="p-4 border rounded-lg transition-colors"
+                         :class="t.is_current ? 'border-indigo-500 bg-indigo-50' : 'border-gray-200 hover:border-gray-300'">
+                        <h4 class="font-semibold text-gray-900" x-text="t.name"></h4>
+                        <p class="text-sm text-gray-500 mt-1" x-text="formatCurrency(t.price_monthly_cents) + '/mo'"></p>
+                        <template x-if="t.is_current">
+                            <span class="inline-block mt-3 px-3 py-1 text-xs font-semibold text-indigo-700 bg-indigo-100 rounded-full">Current Plan</span>
+                        </template>
+                        <template x-if="!t.is_current">
+                            <button @click="changeTier(t.code)"
+                                    :disabled="changingTier"
+                                    class="mt-3 inline-flex items-center px-4 py-2 text-sm font-medium text-white rounded-lg transition-colors disabled:opacity-50"
+                                    :class="t.can_upgrade ? 'bg-indigo-600 hover:bg-indigo-700' : 'bg-gray-600 hover:bg-gray-700'"
+                                    x-text="changingTier ? 'Processing...' : (t.can_upgrade ? 'Upgrade' : 'Downgrade')">
+                            </button>
+                        </template>
+                    </div>
+                </template>
+            </div>
         </div>
 
     </div>
@@ -129,7 +145,8 @@ function merchantSubscriptionDetail() {
         error: null,
         successMessage: null,
         subscription: null,
-        upgrading: false,
+        availableTiers: [],
+        changingTier: false,
 
         init() {
             this.loadSubscription();
@@ -140,8 +157,8 @@ function merchantSubscriptionDetail() {
             return match ? decodeURIComponent(match[1]) : null;
         },
 
-        getSubscriptionId() {
-            // Extract ID from URL: /merchants/billing/subscriptions/{id}
+        getPlatformId() {
+            // Extract platform_id from URL: /merchants/billing/subscriptions/{platform_id}
             const parts = window.location.pathname.split('/');
             return parts[parts.length - 1];
         },
@@ -153,9 +170,9 @@ function merchantSubscriptionDetail() {
                 return;
             }
 
-            const subId = this.getSubscriptionId();
+            const platformId = this.getPlatformId();
             try {
-                const resp = await fetch(`/api/v1/merchants/billing/subscriptions/${subId}`, {
+                const resp = await fetch(`/api/v1/merchants/billing/subscriptions/${platformId}`, {
                     headers: { 'Authorization': `Bearer ${token}` }
                 });
                 if (resp.status === 401) {
@@ -163,40 +180,68 @@ function merchantSubscriptionDetail() {
                     return;
                 }
                 if (!resp.ok) throw new Error('Failed to load subscription');
-                this.subscription = await resp.json();
+                const data = await resp.json();
+                this.subscription = data.subscription || data;
             } catch (err) {
                 console.error('Error:', err);
                 this.error = 'Failed to load subscription details.';
             } finally {
                 this.loading = false;
             }
+
+            // Load available tiers after subscription is loaded
+            await this.loadAvailableTiers(platformId);
         },
 
-        async requestUpgrade() {
-            this.upgrading = true;
+        async loadAvailableTiers(platformId) {
+            const token = this.getToken();
+            if (!token) return;
+
+            try {
+                const resp = await fetch(`/api/v1/merchants/billing/subscriptions/${platformId}/tiers`, {
+                    headers: { 'Authorization': `Bearer ${token}` }
+                });
+                if (!resp.ok) return;
+                const data = await resp.json();
+                this.availableTiers = data.tiers || [];
+            } catch (err) {
+                console.error('Failed to load tiers:', err);
+            }
+        },
+
+        async changeTier(tierCode) {
+            if (!confirm(`Are you sure you want to change your plan to this tier?`)) return;
+
+            this.changingTier = true;
             this.error = null;
             this.successMessage = null;
 
             const token = this.getToken();
-            const subId = this.getSubscriptionId();
+            const platformId = this.getPlatformId();
 
             try {
-                const resp = await fetch(`/api/v1/merchants/billing/subscriptions/${subId}/upgrade`, {
+                const resp = await fetch(`/api/v1/merchants/billing/subscriptions/${platformId}/change-tier`, {
                     method: 'POST',
                     headers: {
                         'Authorization': `Bearer ${token}`,
                         'Content-Type': 'application/json'
-                    }
+                    },
+                    body: JSON.stringify({ tier_code: tierCode, is_annual: this.subscription?.is_annual || false })
                 });
                 if (!resp.ok) {
                     const data = await resp.json();
-                    throw new Error(data.detail || 'Upgrade request failed');
+                    throw new Error(data.detail || 'Failed to change tier');
                 }
-                this.successMessage = 'Upgrade request submitted. You will be contacted with available options.';
+                const result = await resp.json();
+                this.successMessage = result.message || 'Plan changed successfully.';
+
+                // Reload data
+                this.loading = true;
+                await this.loadSubscription();
             } catch (err) {
                 this.error = err.message;
             } finally {
-                this.upgrading = false;
+                this.changingTier = false;
             }
         },
 
@@ -205,6 +250,14 @@ function merchantSubscriptionDetail() {
             return str.charAt(0).toUpperCase() + str.slice(1);
         },
 
+        formatCurrency(cents) {
+            if (cents === null || cents === undefined) return '-';
+            return new Intl.NumberFormat('de-LU', {
+                style: 'currency',
+                currency: 'EUR'
+            }).format(cents / 100);
+        },
+
         formatDate(dateStr) {
             if (!dateStr) return '-';
             return new Date(dateStr).toLocaleDateString('en-GB', { day: 'numeric', month: 'short', year: 'numeric' });
diff --git a/app/modules/billing/templates/billing/merchant/subscriptions.html b/app/modules/billing/templates/billing/merchant/subscriptions.html
index 47609f3e..21b1d1cb 100644
--- a/app/modules/billing/templates/billing/merchant/subscriptions.html
+++ b/app/modules/billing/templates/billing/merchant/subscriptions.html
@@ -57,8 +57,7 @@
                     <template x-for="sub in subscriptions" :key="sub.id">
                         <tr class="text-gray-700 hover:bg-gray-50 transition-colors">
                             <td class="px-6 py-4">
-                                <p class="font-semibold text-gray-900" x-text="sub.platform_name || sub.store_name"></p>
-                                <p class="text-xs text-gray-400" x-text="sub.store_code || ''"></p>
+                                <p class="font-semibold text-gray-900" x-text="sub.platform_name"></p>
                             </td>
                             <td class="px-6 py-4">
                                 <span class="px-2.5 py-1 text-xs font-semibold rounded-full"
@@ -83,7 +82,7 @@
                             </td>
                             <td class="px-6 py-4 text-sm" x-text="formatDate(sub.period_end)"></td>
                             <td class="px-6 py-4 text-right">
-                                <a :href="'/merchants/billing/subscriptions/' + sub.id"
+                                <a :href="'/merchants/billing/subscriptions/' + sub.platform_id"
                                    class="inline-flex items-center px-3 py-1.5 text-sm font-medium text-indigo-600 bg-indigo-50 rounded-lg hover:bg-indigo-100 transition-colors">
                                     View Details
                                 </a>
diff --git a/tests/unit/services/test_billing_service.py b/app/modules/billing/tests/unit/test_billing_service.py
similarity index 100%
rename from tests/unit/services/test_billing_service.py
rename to app/modules/billing/tests/unit/test_billing_service.py
diff --git a/tests/unit/services/test_capacity_forecast_service.py b/app/modules/billing/tests/unit/test_capacity_forecast_service.py
similarity index 100%
rename from tests/unit/services/test_capacity_forecast_service.py
rename to app/modules/billing/tests/unit/test_capacity_forecast_service.py
diff --git a/tests/unit/services/test_stripe_webhook_handler.py b/app/modules/billing/tests/unit/test_stripe_webhook_handler.py
similarity index 100%
rename from tests/unit/services/test_stripe_webhook_handler.py
rename to app/modules/billing/tests/unit/test_stripe_webhook_handler.py
diff --git a/tests/unit/models/database/test_product.py b/app/modules/catalog/tests/unit/test_product_model.py
similarity index 100%
rename from tests/unit/models/database/test_product.py
rename to app/modules/catalog/tests/unit/test_product_model.py
diff --git a/tests/unit/models/schema/test_product.py b/app/modules/catalog/tests/unit/test_product_schema.py
similarity index 100%
rename from tests/unit/models/schema/test_product.py
rename to app/modules/catalog/tests/unit/test_product_schema.py
diff --git a/tests/unit/services/test_store_product_service.py b/app/modules/catalog/tests/unit/test_store_product_service.py
similarity index 100%
rename from tests/unit/services/test_store_product_service.py
rename to app/modules/catalog/tests/unit/test_store_product_service.py
diff --git a/tests/unit/services/test_admin_customer_service.py b/app/modules/customers/tests/unit/test_admin_customer_service.py
similarity index 100%
rename from tests/unit/services/test_admin_customer_service.py
rename to app/modules/customers/tests/unit/test_admin_customer_service.py
diff --git a/tests/unit/services/test_customer_address_service.py b/app/modules/customers/tests/unit/test_customer_address_service.py
similarity index 100%
rename from tests/unit/services/test_customer_address_service.py
rename to app/modules/customers/tests/unit/test_customer_address_service.py
diff --git a/tests/unit/models/database/test_customer.py b/app/modules/customers/tests/unit/test_customer_model.py
similarity index 100%
rename from tests/unit/models/database/test_customer.py
rename to app/modules/customers/tests/unit/test_customer_model.py
diff --git a/tests/unit/models/schema/test_customer.py b/app/modules/customers/tests/unit/test_customer_schema.py
similarity index 100%
rename from tests/unit/models/schema/test_customer.py
rename to app/modules/customers/tests/unit/test_customer_schema.py
diff --git a/tests/unit/models/database/test_inventory.py b/app/modules/inventory/tests/unit/test_inventory_model.py
similarity index 100%
rename from tests/unit/models/database/test_inventory.py
rename to app/modules/inventory/tests/unit/test_inventory_model.py
diff --git a/tests/unit/models/schema/test_inventory.py b/app/modules/inventory/tests/unit/test_inventory_schema.py
similarity index 100%
rename from tests/unit/models/schema/test_inventory.py
rename to app/modules/inventory/tests/unit/test_inventory_schema.py
diff --git a/tests/integration/api/v1/loyalty/test_storefront_loyalty.py b/app/modules/loyalty/tests/integration/test_storefront_loyalty.py
similarity index 100%
rename from tests/integration/api/v1/loyalty/test_storefront_loyalty.py
rename to app/modules/loyalty/tests/integration/test_storefront_loyalty.py
diff --git a/tests/unit/models/database/test_marketplace_import_job.py b/app/modules/marketplace/tests/unit/test_import_job_model.py
similarity index 100%
rename from tests/unit/models/database/test_marketplace_import_job.py
rename to app/modules/marketplace/tests/unit/test_import_job_model.py
diff --git a/tests/unit/models/schema/test_marketplace_import_job.py b/app/modules/marketplace/tests/unit/test_import_job_schema.py
similarity index 100%
rename from tests/unit/models/schema/test_marketplace_import_job.py
rename to app/modules/marketplace/tests/unit/test_import_job_schema.py
diff --git a/tests/unit/services/test_letzshop_service.py b/app/modules/marketplace/tests/unit/test_letzshop_service.py
similarity index 100%
rename from tests/unit/services/test_letzshop_service.py
rename to app/modules/marketplace/tests/unit/test_letzshop_service.py
diff --git a/tests/unit/services/test_marketplace_product_service.py b/app/modules/marketplace/tests/unit/test_marketplace_product_service.py
similarity index 100%
rename from tests/unit/services/test_marketplace_product_service.py
rename to app/modules/marketplace/tests/unit/test_marketplace_product_service.py
diff --git a/tests/unit/services/test_onboarding_service.py b/app/modules/marketplace/tests/unit/test_onboarding_service.py
similarity index 100%
rename from tests/unit/services/test_onboarding_service.py
rename to app/modules/marketplace/tests/unit/test_onboarding_service.py
diff --git a/tests/unit/models/database/test_marketplace_product.py b/app/modules/marketplace/tests/unit/test_product_model.py
similarity index 100%
rename from tests/unit/models/database/test_marketplace_product.py
rename to app/modules/marketplace/tests/unit/test_product_model.py
diff --git a/tests/unit/services/test_product_service.py b/app/modules/marketplace/tests/unit/test_product_service.py
similarity index 100%
rename from tests/unit/services/test_product_service.py
rename to app/modules/marketplace/tests/unit/test_product_service.py
diff --git a/tests/unit/services/test_email_service.py b/app/modules/messaging/tests/unit/test_email_service.py
similarity index 100%
rename from tests/unit/services/test_email_service.py
rename to app/modules/messaging/tests/unit/test_email_service.py
diff --git a/tests/unit/services/test_message_attachment_service.py b/app/modules/messaging/tests/unit/test_message_attachment_service.py
similarity index 100%
rename from tests/unit/services/test_message_attachment_service.py
rename to app/modules/messaging/tests/unit/test_message_attachment_service.py
diff --git a/tests/unit/services/test_messaging_service.py b/app/modules/messaging/tests/unit/test_messaging_service.py
similarity index 100%
rename from tests/unit/services/test_messaging_service.py
rename to app/modules/messaging/tests/unit/test_messaging_service.py
diff --git a/tests/unit/services/test_customer_order_service.py b/app/modules/orders/tests/unit/test_customer_order_service.py
similarity index 100%
rename from tests/unit/services/test_customer_order_service.py
rename to app/modules/orders/tests/unit/test_customer_order_service.py
diff --git a/tests/unit/services/test_invoice_service.py b/app/modules/orders/tests/unit/test_invoice_service.py
similarity index 100%
rename from tests/unit/services/test_invoice_service.py
rename to app/modules/orders/tests/unit/test_invoice_service.py
diff --git a/tests/unit/models/database/test_order_item_exception.py b/app/modules/orders/tests/unit/test_order_item_exception_model.py
similarity index 100%
rename from tests/unit/models/database/test_order_item_exception.py
rename to app/modules/orders/tests/unit/test_order_item_exception_model.py
diff --git a/tests/unit/services/test_order_metrics_customer.py b/app/modules/orders/tests/unit/test_order_metrics_customer.py
similarity index 100%
rename from tests/unit/services/test_order_metrics_customer.py
rename to app/modules/orders/tests/unit/test_order_metrics_customer.py
diff --git a/tests/unit/models/database/test_order.py b/app/modules/orders/tests/unit/test_order_model.py
similarity index 100%
rename from tests/unit/models/database/test_order.py
rename to app/modules/orders/tests/unit/test_order_model.py
diff --git a/tests/unit/models/schema/test_order.py b/app/modules/orders/tests/unit/test_order_schema.py
similarity index 100%
rename from tests/unit/models/schema/test_order.py
rename to app/modules/orders/tests/unit/test_order_schema.py
diff --git a/app/modules/tenancy/static/admin/js/merchant-detail.js b/app/modules/tenancy/static/admin/js/merchant-detail.js
index 538c5886..e0b3fd8e 100644
--- a/app/modules/tenancy/static/admin/js/merchant-detail.js
+++ b/app/modules/tenancy/static/admin/js/merchant-detail.js
@@ -156,11 +156,16 @@ function adminMerchantDetail() {
             }
         },
 
-        // Open create subscription modal
+        // Open create subscription modal (only show platforms without existing subscriptions)
         async openCreateSubscriptionModal() {
-            const firstPlatformId = this.platforms.length > 0 ? this.platforms[0].id : null;
-            this.createForm = { platform_id: firstPlatformId, tier_code: 'essential', status: 'trial', trial_days: 14, is_annual: false };
-            await this.loadTiers(firstPlatformId);
+            const usedPlatformIds = this.subscriptions.map(e => e.platform_id);
+            const available = this.platforms.filter(p => !usedPlatformIds.includes(p.id));
+            if (available.length === 0) {
+                Utils.showToast('All platforms already have subscriptions', 'info');
+                return;
+            }
+            this.createForm = { platform_id: available[0].id, tier_code: 'essential', status: 'trial', trial_days: 14, is_annual: false };
+            await this.loadTiers(available[0].id);
             this.showCreateSubscriptionModal = true;
         },
 
diff --git a/app/modules/tenancy/templates/tenancy/admin/merchant-detail.html b/app/modules/tenancy/templates/tenancy/admin/merchant-detail.html
index 406a6bff..4e4997fc 100644
--- a/app/modules/tenancy/templates/tenancy/admin/merchant-detail.html
+++ b/app/modules/tenancy/templates/tenancy/admin/merchant-detail.html
@@ -320,7 +320,7 @@
                 <select x-model="createForm.platform_id"
                         @change="onCreatePlatformChange()"
                         class="w-full px-3 py-2 text-sm border border-gray-300 rounded-lg dark:border-gray-600 dark:bg-gray-700 dark:text-gray-300 focus:outline-none focus:ring-2 focus:ring-purple-500">
-                    <template x-for="p in platforms" :key="p.id">
+                    <template x-for="p in platforms.filter(p => !subscriptions.some(s => s.platform_id === p.id))" :key="p.id">
                         <option :value="p.id" x-text="p.name"></option>
                     </template>
                 </select>
diff --git a/tests/integration/api/v1/admin/test_merchant_domains.py b/app/modules/tenancy/tests/integration/test_merchant_domains_api.py
similarity index 100%
rename from tests/integration/api/v1/admin/test_merchant_domains.py
rename to app/modules/tenancy/tests/integration/test_merchant_domains_api.py
diff --git a/tests/unit/models/database/test_admin_platform.py b/app/modules/tenancy/tests/unit/test_admin_platform_model.py
similarity index 100%
rename from tests/unit/models/database/test_admin_platform.py
rename to app/modules/tenancy/tests/unit/test_admin_platform_model.py
diff --git a/tests/unit/services/test_admin_platform_service.py b/app/modules/tenancy/tests/unit/test_admin_platform_service.py
similarity index 100%
rename from tests/unit/services/test_admin_platform_service.py
rename to app/modules/tenancy/tests/unit/test_admin_platform_service.py
diff --git a/tests/unit/models/test_merchant_domain.py b/app/modules/tenancy/tests/unit/test_merchant_domain.py
similarity index 100%
rename from tests/unit/models/test_merchant_domain.py
rename to app/modules/tenancy/tests/unit/test_merchant_domain.py
diff --git a/tests/unit/services/test_merchant_domain_service.py b/app/modules/tenancy/tests/unit/test_merchant_domain_service.py
similarity index 100%
rename from tests/unit/services/test_merchant_domain_service.py
rename to app/modules/tenancy/tests/unit/test_merchant_domain_service.py
diff --git a/tests/unit/services/test_store_domain_service.py b/app/modules/tenancy/tests/unit/test_store_domain_service.py
similarity index 100%
rename from tests/unit/services/test_store_domain_service.py
rename to app/modules/tenancy/tests/unit/test_store_domain_service.py
diff --git a/tests/unit/models/database/test_store.py b/app/modules/tenancy/tests/unit/test_store_model.py
similarity index 100%
rename from tests/unit/models/database/test_store.py
rename to app/modules/tenancy/tests/unit/test_store_model.py
diff --git a/tests/unit/models/schema/test_store.py b/app/modules/tenancy/tests/unit/test_store_schema.py
similarity index 100%
rename from tests/unit/models/schema/test_store.py
rename to app/modules/tenancy/tests/unit/test_store_schema.py
diff --git a/tests/unit/services/test_store_service.py b/app/modules/tenancy/tests/unit/test_store_service.py
similarity index 100%
rename from tests/unit/services/test_store_service.py
rename to app/modules/tenancy/tests/unit/test_store_service.py
diff --git a/tests/unit/services/test_store_team_service.py b/app/modules/tenancy/tests/unit/test_store_team_service.py
similarity index 100%
rename from tests/unit/services/test_store_team_service.py
rename to app/modules/tenancy/tests/unit/test_store_team_service.py
diff --git a/tests/unit/models/database/test_team.py b/app/modules/tenancy/tests/unit/test_team_model.py
similarity index 100%
rename from tests/unit/models/database/test_team.py
rename to app/modules/tenancy/tests/unit/test_team_model.py
diff --git a/tests/unit/services/test_team_service.py b/app/modules/tenancy/tests/unit/test_team_service.py
similarity index 100%
rename from tests/unit/services/test_team_service.py
rename to app/modules/tenancy/tests/unit/test_team_service.py
diff --git a/tests/unit/models/database/test_user.py b/app/modules/tenancy/tests/unit/test_user_model.py
similarity index 100%
rename from tests/unit/models/database/test_user.py
rename to app/modules/tenancy/tests/unit/test_user_model.py