Marketplace Commission Motor

The Commission Motor is the back-end that the Seller Dashboard (F11.06) and the buyer-facing storefront both call into. Sellers are onboarded via Stripe Connect Express — the platform creates the connected account, hosts the KYC flow, and stores the account ID; payouts route directly to the seller's bank without funds touching a platform-held balance. Listings are stored as Commission Listings with full i18n support (title, description, attribute labels in 43+ languages), per-variant stock, category taxonomy aligned with Equipment Catalog (F11.01), and pricing in the seller's chosen currency with FX-converted display prices for the buyer.

At checkout, the Transparent Commission Breakdown shows the buyer the item price, shipping, taxes, and a clearly labeled 5% platform commission line — building trust and pre-empting marketplace complaints. The Atomic Stock Decrement uses a database-level conditional update (decrement only if stock >= quantity) to prevent oversell under race conditions when two buyers hit checkout simultaneously; if the decrement fails, the order is rejected with a 'sold out' message and the payment is never captured. On successful payment, Stripe captures the full amount, transfers seller-net to the connected account, and retains the platform fee in the platform balance.

Refunds invoke Proportional Commission Reversal: if a buyer is refunded 60% of a EUR 100 order, the platform refunds 60% of the original commission as well, keeping seller margins consistent. The Monthly Seller Payout Job runs idempotently on the first of each month, computing each seller's net earnings, generating a settlement statement PDF, and triggering payouts; idempotency keys ensure a re-run never double-pays. The Commission Accounting Job produces a monthly financial report (gross merchandise volume, commission earned, refund liability, FX exposure) for platform finance.

Admin endpoints expose commission reports per seller / period and allow manual refund adjustments for dispute resolution.