polar-billing

Polar Billing System

Comprehensive guide to Polar's billing infrastructure, covering entities, flows, Stripe integration, and benefit provisioning.

Quick Reference

Checkout → Payment → Order → Transaction → Benefits
                         ↓
                   Subscription (if recurring)
                         ↓
                   Subscription Cycle → Order → ...

Table of Contents

1. Core Entities
2. Entity Relationships
3. Main Services
4. Dramatiq Background Tasks
5. Stripe Integration
6. Subscription Lifecycle
7. Proration System
8. Benefits & Credits
9. Dunning & Payment Retry
10. Transaction Ledger
11. Key File Locations

---

1. Core Entities

Checkout

File: server/polar/models/checkout.py

Shopping cart/payment session before order confirmation.

Field	Type	Description
status	CheckoutStatus	open, expired, confirmed, succeeded, failed
payment_processor	PaymentProcessor	stripe, manual
client_secret	str	Unique identifier for frontend
amount, currency	int, str	Price in cents
tax_amount, discount_amount	int	Calculated amounts
allow_trial, trial_end	bool, datetime	Trial configuration
seats	int	For seat-based products

Relationships: organization, customer, product, product_price, discount, subscription (for upgrades)

---

Order

File: server/polar/models/order.py

Represents a billing event (one-time purchase or subscription cycle).

Field	Type	Description
status	OrderStatus	pending, paid, refunded, partially_refunded
billing_reason	OrderBillingReason	purchase, subscription_create, subscription_cycle, subscription_update
subtotal_amount	int	Amount before discount/tax
discount_amount	int	Discount applied
tax_amount	int	Tax collected
applied_balance_amount	int	Account balance applied
platform_fee_amount	int	Polar's fee
refunded_amount	int	Already refunded
next_payment_attempt_at	datetime	Dunning retry time

Computed Properties:

• net_amount = subtotal - discount
• total_amount = net + tax
• due_amount = max(0, total + applied_balance)
• payout_amount = net - platform_fee - refunded

---

Subscription

File: server/polar/models/subscription.py

Recurring billing relationship.

Field	Type	Description
status	SubscriptionStatus	incomplete, trialing, active, past_due, canceled, unpaid
amount, currency	int, str	Subscription price
recurring_interval	Interval	month, year
current_period_start/end	datetime	Billing period
trial_start/end	datetime	Trial period
cancel_at_period_end	bool	Scheduled cancellation
canceled_at, ended_at	datetime	Lifecycle timestamps
past_due_at	datetime	When payment failed
seats	int	For seat-based pricing

Relationships: customer, product, payment_method, discount, meters, grants (benefits)

---

Transaction

File: server/polar/models/transaction.py

All money flows in the system.

Field	Type	Description
type	TransactionType	payment, processor_fee, refund, dispute, balance, payout
processor	Processor	stripe, manual
amount, currency	int, str	Transaction amount
tax_amount	int	Tax portion

Self-referential relationships: payment_transaction, balance_transactions, incurred_transactions

---

Payment

File: server/polar/models/payment.py

Individual payment transaction.

Field	Type	Description
status	PaymentStatus	pending, succeeded, failed
processor_id	str	Stripe charge ID
method	str	card, bank_transfer, etc.
decline_reason	str	Why payment failed
risk_level, risk_score	str, int	Fraud assessment

---

Refund

File: server/polar/models/refund.py

Field	Type	Description
status	RefundStatus	pending, succeeded, failed, canceled
reason	RefundReason	duplicate, fraudulent, customer_request, etc.
amount, tax_amount	int	Refund amounts
revoke_benefits	bool	Whether to revoke customer benefits

---

Customer

File: server/polar/models/customer.py

Field	Type	Description
email, name	str	Contact info
stripe_customer_id	str	Stripe link
billing_address	Address	Stored address
tax_id	str	For tax compliance

---

Product & ProductPrice

Files: server/polar/models/product.py, server/polar/models/product_price.py

ProductPrice Types	Description
ProductPriceFixed	Fixed amount
ProductPriceCustom	Merchant sets at checkout
ProductPriceFree	Zero cost
ProductPriceMeteredUnit	Pay-per-unit
ProductPriceSeatUnit	Per-seat with tiers

---

BillingEntry

File: server/polar/models/billing_entry.py

Audit log for billing calculations.

Field	Type	Description
type	BillingEntryType	cycle, proration, metered, seats_increase, seats_decrease
direction	Direction	debit, credit
amount	int	Entry amount

---

2. Entity Relationships

Organization
├── Product
│   ├── ProductPrice (multiple per product)
│   └── ProductBenefit → Benefit
├── Customer
│   ├── Subscription → Product, Discount
│   │   ├── SubscriptionProductPrice
│   │   ├── SubscriptionMeter
│   │   └── BenefitGrant
│   ├── Order → Product, Subscription
│   │   └── OrderItem
│   ├── PaymentMethod
│   └── Wallet
├── Checkout → Customer, Product
├── Discount
│   └── DiscountRedemption
└── Account (for payouts)
    └── Payout → Transaction

Transaction (ledger)
├── payment → Order, Customer
├── refund → Refund, Order
├── dispute → Dispute, Order
├── processor_fee → parent payment
└── payout → Account

---

3. Main Services

SubscriptionService

File: server/polar/subscription/service.py

Core subscription operations:

# Creation
create_or_update_from_checkout(checkout, payment_method) → (Subscription, created)

# Updates
update_product(subscription, product_id, proration_behavior)
update_seats(subscription, seats, proration_behavior)
update_discount(subscription, discount_id)
update_trial(subscription, trial_end)

# Lifecycle
cycle(subscription)  # Period renewal
cancel(subscription)  # At period end
revoke(subscription)  # Immediately
uncancel(subscription)

# Benefits
enqueue_benefits_grants(task="grant"|"revoke", customer, product)

OrderService

File: server/polar/order/service.py

create_from_checkout(checkout)  # One-time purchase
create_subscription_order(subscription, billing_reason)  # Recurring
trigger_payment(order)  # Charge customer
create_order_balance(order)  # Ledger entries

CheckoutService

File: server/polar/checkout/service.py

create(product, customer_data, discount_code)
confirm(checkout)  # Lock checkout for payment
handle_stripe_success(checkout, charge)
handle_free_success(checkout)  # No payment needed

PaymentService

File: server/polar/payment/service.py

upsert_from_stripe_charge(charge, checkout, order)
handle_success(payment)  # Complete order
handle_failure(payment)  # Update order status

RefundService

File: server/polar/refund/service.py

create(order, amount, reason, revoke_benefits)
upsert_from_stripe(stripe_refund)

BenefitGrantService

File: server/polar/benefit/grant/service.py

enqueue_benefits_grants(task, customer, product, order=None, subscription=None)
grant_benefit(customer, benefit)
revoke_benefit(customer, benefit)

---

4. Dramatiq Background Tasks

Subscription Tasks

File: server/polar/subscription/tasks.py

Task	Trigger	Action
subscription.cycle	Scheduler at period end	Renew subscription, create order
subscription.update_product_benefits_grants	Product benefits changed	Update all grants
subscription.cancel_customer	Customer deleted	Cancel all subscriptions

Order Tasks

File: server/polar/order/tasks.py

Task	Trigger	Action
order.create_subscription_order	Subscription cycle	Create billing order
order.trigger_payment	Order ready	Charge payment method
order.balance	Payment success	Create ledger entries
order.invoice	Order created	Generate PDF invoice
order.process_dunning	Hourly cron	Find orders for retry
order.process_dunning_order	Individual retry	Retry single payment

Stripe Webhook Tasks

File: server/polar/integrations/stripe/tasks.py

Task	Stripe Event	Action
charge.succeeded	Payment complete	Create order, provision benefits
charge.failed	Payment failed	Mark order failed
charge.updated	Charge settled	Create ledger transaction
refund.created/updated	Refund processed	Update refund record
charge.dispute.created	Chargeback	Create dispute, revoke benefits
payout.paid	Payout complete	Update payout status

Benefit Tasks

File: server/polar/benefit/tasks.py

Task	Trigger	Action
benefit.enqueue_benefits_grants	Order/subscription	Queue individual grants
benefit.grant	Individual benefit	Provision access (GitHub, Discord, etc.)
benefit.revoke	Cancellation/refund	Remove access
benefit.cycle	Subscription renewal	Reset credits with rollover

Checkout Tasks

File: server/polar/checkout/tasks.py

Task	Trigger	Action
checkout.handle_free_success	Free product	Complete without payment
checkout.expire_open_checkouts	Every 15 min	Mark expired checkouts

Payout Tasks

File: server/polar/payout/tasks.py

Task	Trigger	Action
payout.trigger_stripe_payouts	Daily 00:15 UTC	Initiate pending payouts

---

5. Stripe Integration

Webhook Endpoints

File: server/polar/integrations/stripe/endpoints.py

• /v1/integrations/stripe/webhook - Direct webhooks
• /v1/integrations/stripe/webhook-connect - Connect account webhooks

Implemented Webhooks

Payment Flow:

• payment_intent.succeeded - Payment complete
• payment_intent.payment_failed - Payment failed
• setup_intent.succeeded - Card saved
• charge.pending/failed/succeeded/updated - Charge lifecycle

Refunds:

• refund.created/updated/failed

Disputes:

• charge.dispute.created/updated/closed

Connect:

• account.updated - Account info changed
• payout.updated/paid - Payout lifecycle

Webhook Processing Flow

Stripe POST → Verify signature → ExternalEvent.enqueue()
                                        ↓
                               Store in external_events table
                                        ↓
                               Enqueue Dramatiq task
                                        ↓
                               Worker processes async
                                        ↓
                               Mark handled_at on success

StripeService

File: server/polar/integrations/stripe/service.py

Key methods:

• create_payment_intent(), create_setup_intent()
• create_refund(), get_refund()
• create_tax_calculation(), create_tax_transaction()
• transfer(), create_payout()

---

6. Subscription Lifecycle

Creation Flow

1. Checkout created (status=open)
2. Customer completes payment
3. Stripe charge.succeeded webhook
4. payment.handle_success() called
5. checkout_service.handle_stripe_success()
6. subscription_service.create_or_update_from_checkout()
   - Creates Subscription (status=active or trialing)
   - Sets billing period
   - Applies discount
   - Resets meters
7. Enqueue benefit grants
8. Send confirmation email

Cycle Flow (Renewal)

1. APScheduler triggers at period end
2. subscription.cycle task runs
3. subscription_service.cycle()
   - Check cancel_at_period_end
   - If true: set status=canceled, revoke benefits
   - If false: advance period dates, check discount expiry
4. Create billing entry (type=cycle)
5. Enqueue order.create_subscription_order
6. Order created with billing_reason=subscription_cycle
7. Enqueue order.trigger_payment
8. Stripe charges payment method
9. charge.succeeded → ledger entries → benefits renewed

Cancellation Flow

At Period End:

subscription_service.cancel(subscription)
# Sets cancel_at_period_end=True, ends_at=current_period_end
# Benefits remain until period ends
# On next cycle: status=canceled, benefits revoked

Immediately:

subscription_service.revoke(subscription)
# Sets status=canceled, ended_at=now
# Benefits revoked immediately
# Seats canceled if seat-based

Trial Flow

1. Checkout with trial_end set
2. Subscription created with status=trialing
3. No payment during trial
4. At trial_end, cycle task runs
5. Status transitions to active
6. Order created with billing_reason=subscription_cycle_after_trial
7. First payment charged

---

7. Proration System

When Prorations Occur

1. Product change - Upgrade/downgrade to different tier
2. Seat change - Add/remove seats
3. Interval change - Monthly to yearly

Proration Calculation

# Calculate time remaining in period
pct_remaining = (period_end - now) / (period_end - period_start)

# Old product credit (what they paid but won't use)
old_credit = old_price * old_pct_remaining

# New product debit (what they owe for remainder)
new_debit = new_price * new_pct_remaining

# Net proration
net = new_debit - old_credit

Proration Behaviors

Behavior	Action
prorate	Add to next invoice
invoice	Create order immediately

BillingEntry for Prorations

# Credit entry (old product)
BillingEntry(
    type=BillingEntryType.proration,
    direction=BillingEntryDirection.credit,
    amount=prorated_old_amount
)

# Debit entry (new product)
BillingEntry(
    type=BillingEntryType.proration,
    direction=BillingEntryDirection.debit,
    amount=prorated_new_amount
)

Seat Proration

# Adding 2 seats at $10/seat with 50% time remaining
delta_amount = 2 * $10 * 0.5 = $10

BillingEntry(
    type=BillingEntryType.subscription_seats_increase,
    direction=BillingEntryDirection.debit,
    amount=1000  # cents
)

---

8. Benefits & Credits

Benefit Types

Type	Description	Grant Action
meter_credit	Usage allowances	Create meter_credited event
github_repository	Repo access	Add to GitHub team
discord	Server role	Assign Discord role
license_keys	License distribution	Generate key
downloadables	File access	Grant download permission
custom	Webhook-based	Call external URL

Benefit Grant Flow

1. Order/Subscription created
2. enqueue_benefits_grants(task="grant")
3. For each benefit in product:
   - Skip if already granted
   - Enqueue benefit.grant task
4. benefit.grant task:
   - Get/create BenefitGrant record
   - Call strategy.grant() (type-specific)
   - Set granted_at
   - Store properties
   - Send webhook

Benefit Revocation Flow

1. Subscription canceled or order refunded
2. enqueue_benefits_grants(task="revoke")
3. For each granted benefit:
   - Enqueue benefit.revoke task
4. benefit.revoke task:
   - Call strategy.revoke() (type-specific)
   - Set revoked_at
   - Send webhook

Meter Credits

Grant:

# Create event with units
Event(type="meter_credited", units=100)
# Update CustomerMeter

Cycle (renewal):

# Calculate rollover
rollover = min(remaining_units, rollover_limit)
# Reset meter
Event(type="meter_reset")
# Credit new period + rollover
Event(type="meter_credited", units=base_units + rollover)

Revoke:

# Negative credit event
Event(type="meter_credited", units=-remaining_units)

Grace Period

Organizations can configure benefit_revocation_grace_period (days) to delay benefit revocation for past_due subscriptions.

---

9. Dunning & Payment Retry

Dunning Process

1. order.process_dunning runs hourly
2. Finds orders where next_payment_attempt_at <= now
3. For each order:
   - Enqueue order.process_dunning_order
4. process_dunning_order:
   - Get customer's payment method
   - Attempt payment via Stripe
   - On success: mark order paid
   - On failure: schedule next attempt

Retry Schedule

Configured in organization settings. Typical pattern:

• Day 1: First failure
• Day 3: Retry 1
• Day 5: Retry 2
• Day 7: Final retry, then mark unpaid

Subscription Status During Dunning

payment fails → status=past_due, past_due_at=now
               ↓
         benefits may continue (grace period)
               ↓
         retry succeeds → status=active
               ↓
         retry fails → status=unpaid, benefits revoked

---

10. Transaction Ledger

Transaction Types

Type	Description
payment	Customer payment received
processor_fee	Stripe fees
refund	Money returned to customer
refund_reversal	Refund failed/reversed
dispute	Chargeback loss
dispute_reversal	Won dispute
balance	Internal balance transfer
payout	Money sent to creator

Creating Payment Transactions

1. charge.updated webhook (charge settled)
2. Get balance_transaction from Stripe
3. Extract settlement amount and fees
4. Create Transaction(type=payment)
5. Enqueue processor_fee.create_payment_fees
6. Create Transaction(type=processor_fee)

Payout Flow

1. Creator has balance from transactions
2. payout.trigger_stripe_payouts (daily)
3. Calculate available balance
4. Create Payout record
5. stripe_service.transfer() to Connect account
6. stripe_service.create_payout() to bank
7. payout.paid webhook → update status

---

11. Key File Locations

Models

server/polar/models/
├── checkout.py
├── order.py
├── order_item.py
├── subscription.py
├── subscription_product_price.py
├── transaction.py
├── payment.py
├── refund.py
├── dispute.py
├── payout.py
├── customer.py
├── product.py
├── product_price.py
├── discount.py
├── benefit.py
├── benefit_grant.py
└── billing_entry.py

Services

server/polar/
├── subscription/service.py
├── order/service.py
├── checkout/service.py
├── payment/service.py
├── refund/service.py
├── dispute/service.py
├── payout/service.py
├── benefit/
│   ├── service.py
│   ├── grant/service.py
│   └── strategies/
│       ├── meter_credit/service.py
│       ├── github_repository/service.py
│       ├── discord/service.py
│       └── ...
└── transaction/service/
    ├── payment.py
    ├── refund.py
    └── dispute.py

Background Tasks

server/polar/
├── subscription/tasks.py
├── order/tasks.py
├── checkout/tasks.py
├── benefit/tasks.py
├── payout/tasks.py
└── integrations/stripe/tasks.py

Stripe Integration

server/polar/integrations/stripe/
├── endpoints.py    # Webhook handlers
├── service.py      # Stripe API wrapper
├── tasks.py        # Webhook processing tasks
└── payment.py      # Payment resolution helpers

---

Common Debugging Scenarios

Payment Failed

1. Check Payment record for decline_reason
2. Check Order.status and next_payment_attempt_at
3. Look at external_events for Stripe webhook

Benefits Not Granted

1. Check BenefitGrant record for errors
2. Look at benefit.grant task in Dramatiq logs
3. Verify product has benefits attached

Proration Issues

1. Check BillingEntry records for subscription
2. Verify billing_reason on Order
3. Check subscription's current_period dates

Subscription Not Cycling

1. Check scheduler_locked_at on subscription
2. Verify APScheduler is running
3. Check subscription.cycle task logs