diff --git a/docs/features/subscription-billing.md b/docs/features/subscription-billing.md
index 3f14e65e..817a8fd7 100644
--- a/docs/features/subscription-billing.md
+++ b/docs/features/subscription-billing.md
@@ -11,6 +11,8 @@ The billing system enables:
 - **Stripe Integration**: Checkout sessions, customer portal, and webhook handling
 - **Self-Service Billing**: Vendor-facing billing page for subscription management
 - **Add-ons**: Optional purchasable items (domains, SSL, email packages)
+- **Capacity Forecasting**: Growth trends and scaling recommendations
+- **Background Jobs**: Automated subscription lifecycle management
 
 ## Architecture
 
@@ -26,23 +28,32 @@ All subscription models are defined in `models/database/subscription.py`:
 | `VendorAddOn` | Add-ons purchased by each vendor |
 | `StripeWebhookEvent` | Idempotency tracking for webhooks |
 | `BillingHistory` | Invoice and payment history |
+| `CapacitySnapshot` | Daily platform capacity metrics for forecasting |
 
 ### Services
 
 | Service | Location | Purpose |
 |---------|----------|---------|
 | `BillingService` | `app/services/billing_service.py` | Subscription operations, checkout, portal |
-| `SubscriptionService` | `app/services/subscription_service.py` | Limit checks, usage tracking |
+| `SubscriptionService` | `app/services/subscription_service.py` | Limit checks, usage tracking, tier info |
 | `StripeService` | `app/services/stripe_service.py` | Core Stripe API operations |
+| `CapacityForecastService` | `app/services/capacity_forecast_service.py` | Growth trends, projections |
+| `PlatformHealthService` | `app/services/platform_health_service.py` | Subscription capacity aggregation |
 
-### Handlers
+### Background Tasks
 
-| Handler | Location | Purpose |
-|---------|----------|---------|
-| `StripeWebhookHandler` | `app/handlers/stripe_webhook.py` | Webhook event processing |
+| Task | Location | Schedule | Purpose |
+|------|----------|----------|---------|
+| `reset_period_counters` | `app/tasks/subscription_tasks.py` | Daily | Reset order counters at period end |
+| `check_trial_expirations` | `app/tasks/subscription_tasks.py` | Daily | Expire trials without payment method |
+| `sync_stripe_status` | `app/tasks/subscription_tasks.py` | Hourly | Sync status with Stripe |
+| `cleanup_stale_subscriptions` | `app/tasks/subscription_tasks.py` | Weekly | Clean up old cancelled subscriptions |
+| `capture_capacity_snapshot` | `app/tasks/subscription_tasks.py` | Daily | Capture capacity metrics snapshot |
 
 ### API Endpoints
 
+#### Vendor Billing API
+
 All billing endpoints are under `/api/v1/vendor/billing`:
 
 | Endpoint | Method | Purpose |
@@ -52,11 +63,28 @@ All billing endpoints are under `/api/v1/vendor/billing`:
 | `/billing/checkout` | POST | Create Stripe checkout session |
 | `/billing/portal` | POST | Create Stripe customer portal session |
 | `/billing/invoices` | GET | Invoice history |
+| `/billing/upcoming-invoice` | GET | Preview next invoice |
+| `/billing/change-tier` | POST | Upgrade/downgrade tier |
 | `/billing/addons` | GET | Available add-on products |
 | `/billing/my-addons` | GET | Vendor's purchased add-ons |
+| `/billing/addons/purchase` | POST | Purchase an add-on |
+| `/billing/addons/{id}` | DELETE | Cancel an add-on |
 | `/billing/cancel` | POST | Cancel subscription |
 | `/billing/reactivate` | POST | Reactivate cancelled subscription |
 
+#### Admin Platform Health API
+
+Capacity endpoints under `/api/v1/admin/platform-health`:
+
+| Endpoint | Method | Purpose |
+|----------|--------|---------|
+| `/platform-health/health` | GET | Full platform health report |
+| `/platform-health/capacity` | GET | Capacity-focused metrics |
+| `/platform-health/subscription-capacity` | GET | Subscription-based capacity vs usage |
+| `/platform-health/trends` | GET | Growth trends over time |
+| `/platform-health/recommendations` | GET | Scaling recommendations |
+| `/platform-health/snapshot` | POST | Manually capture capacity snapshot |
+
 ## Subscription Tiers
 
 ### Default Tiers
@@ -68,6 +96,32 @@ All billing endpoints are under `/api/v1/vendor/billing`:
 | Business | €199/mo | Unlimited | 2000 | 10 |
 | Enterprise | Custom | Unlimited | Unlimited | Unlimited |
 
+### Database-Driven Tiers
+
+Tiers are stored in the `subscription_tiers` table and queried via `SubscriptionService`:
+
+```python
+# Get tier from database with legacy fallback
+tier_info = subscription_service.get_tier_info("professional", db=db)
+
+# Query all active tiers
+all_tiers = subscription_service.get_all_tiers(db=db)
+```
+
+The service maintains backward compatibility with a legacy fallback:
+
+```python
+def get_tier_info(self, tier_code: str, db: Session | None = None) -> TierInfo:
+    """Get full tier information. Queries database if db session provided."""
+    if db is not None:
+        db_tier = self.get_tier_by_code(db, tier_code)
+        if db_tier:
+            return TierInfo(...)
+
+    # Fallback to hardcoded TIER_LIMITS during migration
+    return self._get_tier_from_legacy(tier_code)
+```
+
 ### Tier Features
 
 Each tier includes specific features stored in the `features` JSON column:
@@ -150,6 +204,7 @@ The vendor billing page is at `/vendor/{vendor_code}/billing`:
 3. **Change Plan**: Upgrade/downgrade options
 4. **Payment Method**: Link to Stripe portal
 5. **Invoice History**: Recent invoices with PDF links
+6. **Add-ons**: Available and purchased add-ons
 
 ### JavaScript Component
 
@@ -161,6 +216,8 @@ function billingData() {
         subscription: null,
         tiers: [],
         invoices: [],
+        addons: [],
+        myAddons: [],
 
         async init() {
             await this.loadData();
@@ -177,6 +234,18 @@ function billingData() {
         async openPortal() {
             const response = await this.apiPost('/billing/portal', {});
             window.location.href = response.portal_url;
+        },
+
+        async purchaseAddon(addon) {
+            const response = await this.apiPost('/billing/addons/purchase', {
+                addon_code: addon.code
+            });
+            window.location.href = response.checkout_url;
+        },
+
+        async cancelAddon(addon) {
+            await this.apiDelete(`/billing/addons/${addon.id}`);
+            await this.loadMyAddons();
         }
     };
 }
@@ -201,6 +270,163 @@ function billingData() {
 3. Create Stripe checkout session with add-on price
 4. On webhook success: create `VendorAddOn` record
 
+## Background Tasks
+
+### Task Definitions
+
+```python
+# app/tasks/subscription_tasks.py
+
+async def reset_period_counters():
+    """
+    Reset order counters for subscriptions whose billing period has ended.
+    Should run daily. Resets orders_this_period to 0 and updates period dates.
+    """
+
+async def check_trial_expirations():
+    """
+    Check for expired trials and update their status.
+    Trials without payment method -> expired
+    Trials with payment method -> active
+    """
+
+async def sync_stripe_status():
+    """
+    Sync subscription status with Stripe.
+    Fetches current status and updates local records.
+    """
+
+async def cleanup_stale_subscriptions():
+    """
+    Clean up subscriptions in inconsistent states.
+    Marks old cancelled subscriptions as expired.
+    """
+
+async def capture_capacity_snapshot():
+    """
+    Capture a daily snapshot of platform capacity metrics.
+    Used for growth trending and capacity forecasting.
+    """
+```
+
+### Scheduling
+
+Configure with your scheduler of choice (Celery, APScheduler, cron):
+
+```python
+# Example with APScheduler
+scheduler.add_job(reset_period_counters, 'cron', hour=0, minute=5)
+scheduler.add_job(check_trial_expirations, 'cron', hour=1, minute=0)
+scheduler.add_job(sync_stripe_status, 'cron', minute=0)  # Every hour
+scheduler.add_job(cleanup_stale_subscriptions, 'cron', day_of_week=0)  # Weekly
+scheduler.add_job(capture_capacity_snapshot, 'cron', hour=0, minute=0)
+```
+
+## Capacity Forecasting
+
+### Subscription-Based Capacity
+
+Track theoretical vs actual capacity:
+
+```python
+capacity = platform_health_service.get_subscription_capacity(db)
+
+# Returns:
+{
+    "total_subscriptions": 150,
+    "tier_distribution": {
+        "essential": 80,
+        "professional": 50,
+        "business": 18,
+        "enterprise": 2
+    },
+    "products": {
+        "actual": 125000,
+        "theoretical_limit": 500000,
+        "utilization_percent": 25.0,
+        "headroom": 375000
+    },
+    "orders_monthly": {
+        "actual": 45000,
+        "theoretical_limit": 300000,
+        "utilization_percent": 15.0
+    },
+    "team_members": {
+        "actual": 320,
+        "theoretical_limit": 1500,
+        "utilization_percent": 21.3
+    }
+}
+```
+
+### Growth Trends
+
+Analyze growth over time:
+
+```python
+trends = capacity_forecast_service.get_growth_trends(db, days=30)
+
+# Returns:
+{
+    "period_days": 30,
+    "snapshots_available": 30,
+    "trends": {
+        "vendors": {
+            "start_value": 140,
+            "current_value": 150,
+            "change": 10,
+            "growth_rate_percent": 7.14,
+            "daily_growth_rate": 0.238,
+            "monthly_projection": 161
+        },
+        "products": {
+            "start_value": 115000,
+            "current_value": 125000,
+            "change": 10000,
+            "growth_rate_percent": 8.7,
+            "monthly_projection": 136000
+        }
+    }
+}
+```
+
+### Scaling Recommendations
+
+Get automated scaling advice:
+
+```python
+recommendations = capacity_forecast_service.get_scaling_recommendations(db)
+
+# Returns:
+[
+    {
+        "category": "capacity",
+        "severity": "warning",
+        "title": "Product capacity approaching limit",
+        "description": "Currently at 85% of theoretical product capacity",
+        "action": "Consider upgrading vendor tiers or adding capacity"
+    },
+    {
+        "category": "infrastructure",
+        "severity": "info",
+        "title": "Current tier: Medium",
+        "description": "Next upgrade trigger: 300 vendors",
+        "action": "Monitor growth and plan for infrastructure scaling"
+    }
+]
+```
+
+### Infrastructure Scaling Reference
+
+| Clients | vCPU | RAM | Storage | Database | Monthly Cost |
+|---------|------|-----|---------|----------|--------------|
+| 1-50 | 2 | 4GB | 100GB | SQLite | €30 |
+| 50-100 | 4 | 8GB | 250GB | PostgreSQL | €80 |
+| 100-300 | 4 | 16GB | 500GB | PostgreSQL | €150 |
+| 300-500 | 8 | 32GB | 1TB | PostgreSQL + Redis | €350 |
+| 500-1000 | 16 | 64GB | 2TB | PostgreSQL + Redis | €700 |
+| 1000+ | 32+ | 128GB+ | 4TB+ | PostgreSQL cluster | €1,500+ |
+
 ## Exception Handling
 
 Custom exceptions for billing operations (`app/exceptions/billing.py`):
@@ -252,6 +478,43 @@ def seed_subscription_tiers(op):
     ])
 ```
 
+### Capacity Snapshots Table
+
+The `capacity_snapshots` table stores daily metrics:
+
+```python
+# alembic/versions/l0a1b2c3d4e5_add_capacity_snapshots_table.py
+class CapacitySnapshot(Base):
+    id: int
+    snapshot_date: datetime  # Unique per day
+
+    # Vendor metrics
+    total_vendors: int
+    active_vendors: int
+    trial_vendors: int
+
+    # Subscription metrics
+    total_subscriptions: int
+    active_subscriptions: int
+
+    # Resource metrics
+    total_products: int
+    total_orders_month: int
+    total_team_members: int
+
+    # Storage metrics
+    storage_used_gb: Decimal
+    db_size_mb: Decimal
+
+    # Capacity metrics
+    theoretical_products_limit: int
+    theoretical_orders_limit: int
+    theoretical_team_limit: int
+
+    # Tier distribution
+    tier_distribution: dict  # JSON
+```
+
 ### Setting Up Stripe
 
 1. Create products and prices in Stripe Dashboard
@@ -273,3 +536,10 @@ tier.stripe_price_annual_id = "price_yyy"
 - Idempotency keys prevent duplicate event processing
 - Customer portal links are session-based and expire
 - Stripe API key stored securely in environment variables
+- Background tasks run with database session isolation
+
+## Related Documentation
+
+- [Capacity Monitoring](../operations/capacity-monitoring.md) - Detailed monitoring guide
+- [Capacity Planning](../architecture/capacity-planning.md) - Infrastructure sizing
+- [Stripe Integration](../deployment/stripe-integration.md) - Payment setup for vendors
diff --git a/docs/operations/capacity-monitoring.md b/docs/operations/capacity-monitoring.md
index f46625f5..7913d807 100644
--- a/docs/operations/capacity-monitoring.md
+++ b/docs/operations/capacity-monitoring.md
@@ -1,10 +1,28 @@
 # Capacity Monitoring
 
-Detailed guide for monitoring and managing platform capacity.
+Detailed guide for monitoring and managing platform capacity, including growth forecasting and scaling recommendations.
 
 ## Overview
 
-The Capacity Monitoring page (`/admin/platform-health/capacity`) provides insights into resource consumption and helps plan infrastructure scaling.
+The Capacity Monitoring system provides insights into resource consumption and helps plan infrastructure scaling. It includes:
+
+- **Real-time metrics**: Current resource usage and health status
+- **Subscription capacity**: Theoretical vs actual capacity based on vendor subscriptions
+- **Growth forecasting**: Historical trends and future projections
+- **Scaling recommendations**: Automated advice for infrastructure planning
+
+## API Endpoints
+
+All capacity endpoints are under `/api/v1/admin/platform-health`:
+
+| Endpoint | Method | Description |
+|----------|--------|-------------|
+| `/health` | GET | Full platform health report |
+| `/capacity` | GET | Capacity-focused metrics |
+| `/subscription-capacity` | GET | Subscription-based capacity analysis |
+| `/trends` | GET | Growth trends over specified period |
+| `/recommendations` | GET | Prioritized scaling recommendations |
+| `/snapshot` | POST | Manually capture capacity snapshot |
 
 ## Key Metrics
 
@@ -17,6 +35,41 @@ The Capacity Monitoring page (`/admin/platform-health/capacity`) provides insigh
 | Products per Client | Average products per vendor | Tier compliance |
 | Monthly Orders | Order volume this month | Performance impact |
 
+### Subscription Capacity
+
+Track theoretical vs actual capacity based on all vendor subscriptions:
+
+```python
+# GET /api/v1/admin/platform-health/subscription-capacity
+{
+    "total_subscriptions": 150,
+    "tier_distribution": {
+        "essential": 80,
+        "professional": 50,
+        "business": 18,
+        "enterprise": 2
+    },
+    "products": {
+        "actual": 125000,
+        "theoretical_limit": 500000,
+        "utilization_percent": 25.0,
+        "headroom": 375000
+    },
+    "orders_monthly": {
+        "actual": 45000,
+        "theoretical_limit": 300000,
+        "utilization_percent": 15.0,
+        "headroom": 255000
+    },
+    "team_members": {
+        "actual": 320,
+        "theoretical_limit": 1500,
+        "utilization_percent": 21.3,
+        "headroom": 1180
+    }
+}
+```
+
 ### Storage Metrics
 
 | Metric | Description | Warning | Critical |
@@ -35,26 +88,148 @@ The Capacity Monitoring page (`/admin/platform-health/capacity`) provides insigh
 | Cache Hit Rate | > 90% | 70-90% | < 70% |
 | Connection Pool Usage | < 70% | 70-90% | > 90% |
 
+## Growth Forecasting
+
+### Capacity Snapshots
+
+Daily snapshots are captured automatically by the `capture_capacity_snapshot` background task:
+
+```python
+# Captured daily at midnight
+class CapacitySnapshot:
+    snapshot_date: datetime
+
+    # Vendor metrics
+    total_vendors: int
+    active_vendors: int
+    trial_vendors: int
+
+    # Subscription metrics
+    total_subscriptions: int
+    active_subscriptions: int
+
+    # Resource metrics
+    total_products: int
+    total_orders_month: int
+    total_team_members: int
+
+    # Storage metrics
+    storage_used_gb: Decimal
+    db_size_mb: Decimal
+
+    # Capacity metrics
+    theoretical_products_limit: int
+    theoretical_orders_limit: int
+    theoretical_team_limit: int
+
+    # Tier distribution
+    tier_distribution: dict
+```
+
+### Growth Trends
+
+Analyze growth over any period:
+
+```python
+# GET /api/v1/admin/platform-health/trends?days=30
+{
+    "period_days": 30,
+    "snapshots_available": 30,
+    "start_date": "2025-11-26",
+    "end_date": "2025-12-26",
+    "trends": {
+        "vendors": {
+            "start_value": 140,
+            "current_value": 150,
+            "change": 10,
+            "growth_rate_percent": 7.14,
+            "daily_growth_rate": 0.238,
+            "monthly_projection": 161
+        },
+        "products": {
+            "start_value": 115000,
+            "current_value": 125000,
+            "change": 10000,
+            "growth_rate_percent": 8.7,
+            "daily_growth_rate": 0.29,
+            "monthly_projection": 136000
+        },
+        "orders": {
+            "start_value": 40000,
+            "current_value": 45000,
+            "change": 5000,
+            "growth_rate_percent": 12.5,
+            "monthly_projection": 51000
+        },
+        "team_members": {...},
+        "storage_gb": {
+            "start_value": 150.5,
+            "current_value": 165.2,
+            "change": 14.7
+        }
+    }
+}
+```
+
+### Days Until Threshold
+
+Calculate when a metric will reach a specific threshold:
+
+```python
+# Service method
+days = capacity_forecast_service.get_days_until_threshold(
+    db,
+    metric="total_products",
+    threshold=500000
+)
+# Returns: 120 (days until products reach 500K)
+```
+
 ## Scaling Recommendations
 
-The system provides automatic scaling recommendations based on current usage:
-
-### Example Recommendations
+The system generates automated recommendations based on current capacity and growth:
 
+```python
+# GET /api/v1/admin/platform-health/recommendations
+[
+    {
+        "category": "capacity",
+        "severity": "warning",
+        "title": "Product capacity approaching limit",
+        "description": "Currently at 85% of theoretical product capacity",
+        "action": "Consider upgrading vendor tiers or adding capacity"
+    },
+    {
+        "category": "infrastructure",
+        "severity": "info",
+        "title": "Current tier: Medium",
+        "description": "Next upgrade trigger: 300 vendors",
+        "action": "Monitor growth and plan for infrastructure scaling"
+    },
+    {
+        "category": "growth",
+        "severity": "info",
+        "title": "High vendor growth rate",
+        "description": "Vendor base growing at 15.2% over last 30 days",
+        "action": "Ensure infrastructure can scale to meet demand"
+    },
+    {
+        "category": "storage",
+        "severity": "warning",
+        "title": "Storage usage high",
+        "description": "Image storage at 850 GB",
+        "action": "Plan for storage expansion or implement cleanup policies"
+    }
+]
 ```
-Current Infrastructure: MEDIUM (100-300 clients)
-Current Usage: 85% of capacity
 
-Recommendations:
-1. [WARNING] Approaching product limit (420K of 500K)
-   → Consider upgrading to LARGE tier
+### Severity Levels
 
-2. [INFO] Database size growing 5GB/month
-   → Plan storage expansion in 3 months
-
-3. [OK] API response times within normal range
-   → No action needed
-```
+| Severity | Description | Action Required |
+|----------|-------------|-----------------|
+| `critical` | Immediate action needed | Within 24 hours |
+| `warning` | Plan action soon | Within 1-2 weeks |
+| `info` | Informational | Monitor and plan |
 
 ## Threshold Configuration
 
@@ -90,13 +265,63 @@ CAPACITY_THRESHOLDS = {
 }
 ```
 
-## Historical Trends
+## Infrastructure Scaling Reference
 
-View growth trends to plan ahead:
+| Clients | vCPU | RAM | Storage | Database | Monthly Cost |
+|---------|------|-----|---------|----------|--------------|
+| 1-50 | 2 | 4GB | 100GB | SQLite | €30 |
+| 50-100 | 4 | 8GB | 250GB | PostgreSQL | €80 |
+| 100-300 | 4 | 16GB | 500GB | PostgreSQL | €150 |
+| 300-500 | 8 | 32GB | 1TB | PostgreSQL + Redis | €350 |
+| 500-1000 | 16 | 64GB | 2TB | PostgreSQL + Redis | €700 |
+| 1000+ | 32+ | 128GB+ | 4TB+ | PostgreSQL cluster | €1,500+ |
 
-- **30-day growth rate**: Products, storage, clients
-- **Projected capacity date**: When limits will be reached
-- **Seasonal patterns**: Order volume fluctuations
+## Background Tasks
+
+### Capacity Snapshot Task
+
+```python
+# app/tasks/subscription_tasks.py
+
+async def capture_capacity_snapshot():
+    """
+    Capture a daily snapshot of platform capacity metrics.
+    Should run daily at midnight.
+    """
+    from app.services.capacity_forecast_service import capacity_forecast_service
+
+    db = SessionLocal()
+    try:
+        snapshot = capacity_forecast_service.capture_daily_snapshot(db)
+        db.commit()
+        return {
+            "snapshot_id": snapshot.id,
+            "snapshot_date": snapshot.snapshot_date.isoformat(),
+            "total_vendors": snapshot.total_vendors,
+            "total_products": snapshot.total_products,
+        }
+    finally:
+        db.close()
+```
+
+### Manual Snapshot
+
+Capture a snapshot on demand:
+
+```bash
+# Via API
+curl -X POST /api/v1/admin/platform-health/snapshot \
+  -H "Authorization: Bearer $TOKEN"
+
+# Response
+{
+    "id": 42,
+    "snapshot_date": "2025-12-26T00:00:00Z",
+    "total_vendors": 150,
+    "total_products": 125000,
+    "message": "Snapshot captured successfully"
+}
+```
 
 ## Alerts
 
@@ -106,6 +331,29 @@ Capacity alerts trigger when:
 2. **Critical (Red)**: 95% of any threshold
 3. **Exceeded**: 100%+ of threshold (immediate action)
 
+## Historical Data
+
+### Viewing Historical Trends
+
+Use the `/trends` endpoint with different day ranges:
+
+```bash
+# Last 7 days
+GET /api/v1/admin/platform-health/trends?days=7
+
+# Last 30 days (default)
+GET /api/v1/admin/platform-health/trends?days=30
+
+# Last 90 days
+GET /api/v1/admin/platform-health/trends?days=90
+```
+
+### Data Retention
+
+- Snapshots are stored indefinitely by default
+- Consider implementing cleanup for snapshots older than 2 years
+- At minimum, keep monthly aggregates for long-term trending
+
 ## Export Reports
 
 Generate capacity reports for planning:
@@ -114,8 +362,47 @@ Generate capacity reports for planning:
 - **Monthly capacity report**: Detailed analysis
 - **Projection report**: 3/6/12 month forecasts
 
+## Usage Examples
+
+### Check Current Capacity
+
+```python
+from app.services.platform_health_service import platform_health_service
+from app.services.capacity_forecast_service import capacity_forecast_service
+
+# Get subscription capacity
+capacity = platform_health_service.get_subscription_capacity(db)
+print(f"Products: {capacity['products']['actual']} / {capacity['products']['theoretical_limit']}")
+print(f"Utilization: {capacity['products']['utilization_percent']}%")
+
+# Get growth trends
+trends = capacity_forecast_service.get_growth_trends(db, days=30)
+print(f"Vendor growth: {trends['trends']['vendors']['growth_rate_percent']}%")
+
+# Get recommendations
+recommendations = capacity_forecast_service.get_scaling_recommendations(db)
+for rec in recommendations:
+    print(f"[{rec['severity']}] {rec['title']}: {rec['action']}")
+```
+
+### Project Future Capacity
+
+```python
+# Calculate days until product limit
+days = capacity_forecast_service.get_days_until_threshold(
+    db,
+    metric="total_products",
+    threshold=500000
+)
+if days:
+    print(f"Products will reach 500K in approximately {days} days")
+else:
+    print("Insufficient data or no growth detected")
+```
+
 ## Related Documentation
 
+- [Subscription & Billing](../features/subscription-billing.md) - Complete billing system
 - [Capacity Planning](../architecture/capacity-planning.md) - Full sizing guide
 - [Platform Health](platform-health.md) - Real-time health monitoring
 - [Image Storage](image-storage.md) - Image system details