Buy Now Pay Later (BNPL) Ledger Logic

BNPL is a hybrid of payments and lending. A $100 purchase creates a $100 Merchant Payout (immediate) and a $100 Consumer Loan split into 4 installments of $25. The ledger must link these distinct entities. The complexity is the high velocity; a user might have 20 active micro-loans, each with its own schedule.

The Installment Object Structure

Instead of one loan, the database tracks Installments.

Loan_ID: 101

Installment_1: $25 | Due: T+0 | Status: Paid

Installment_2: $25 | Due: T+14 | Status: Scheduled

Installment_3: $25 | Due: T+28 | Status: Scheduled

Payment Routing: When a user pays $50, the "Allocation Engine" must intelligently apply it to the oldest due installments across multiple active loans.

Late Fee Triggering Logic

Automation is key to unit economics.

The Cron Job: Runs nightly. Checks WHERE due_date < today AND status != 'paid'.

The Action:

Transition Installment to Overdue.

Create new Ledger Entry: Debit: User_Account | Credit: Late_Fee_Revenue.

Trigger email notification.

Freeze user from making new purchases (Risk Control).