Payment Processing Software Development

Payment gateway integration connecting to Stripe, Adyen, Braintree, Worldpay, or direct acquirers through their APIs with the payment method types -- card, bank transfer, digital wallet, and local payment methods -- configured per gateway and per market. Multi-gateway routing directing payment transactions to the optimal gateway based on the payment method, the transaction currency, the issuer country, or the merchant category, with fallback routing to a secondary gateway when the primary gateway is unavailable. Gateway-agnostic transaction management maintaining a unified transaction record regardless of which gateway processed the payment, so reporting, reconciliation, and customer service queries don't require identifying which gateway was used for each transaction. Idempotency handling ensuring that a payment request submitted more than once -- due to network timeout, client retry, or integration error -- creates only one payment transaction rather than duplicating the charge. Webhook processing consuming payment status events from each gateway and updating the transaction record and the downstream systems in real time rather than through polling.

Multi-currency transaction processing accepting payments in the customer's local currency and settling to the merchant in their preferred settlement currency, with the FX conversion applied at the point of settlement using the exchange rate source and margin configured for the product. Real-time FX rate integration pulling rates from a currency data provider or from the payment gateway's FX service, with the rate applied to each transaction recorded against the transaction for audit and for customer disclosure where the product requires it. Multi-currency ledger maintaining separate currency balances for each account or merchant -- the GBP balance, the EUR balance, and the USD balance tracked separately without currency blending. FX settlement calculation producing the settlement amount in the target currency from the collected transactions, with the conversion applied at the configured rate and the settlement reconciliation matching the converted amount against the bank account receipt. FX exposure reporting showing the current currency position across all balances and the unrealised FX gain or loss at the current rate for treasury management.

Reconciliation engine matching incoming bank statement transactions against payment gateway settlement reports and the internal ledger, identifying the payment batch or individual transaction that each bank credit corresponds to and marking matched items as reconciled without manual intervention. Exception queue presenting unmatched or partially matched items to the reconciliation team for manual review, with each exception showing the bank statement entry, the nearest matching gateway settlement record, and the amount and date discrepancy, rather than requiring the team to identify the exception themselves from an unfiltered transaction list. Daily reconciliation report showing the reconciled and unreconciled positions across all payment methods and currencies, produced automatically at the configured time each day so the finance team sees the current position without running a manual report. Tolerance handling for reconciliation items where the discrepancy is below a configured threshold -- typically caused by FX rounding -- automatically marking low-value discrepancies as reconciled within tolerance rather than adding them to the exception queue. Historical reconciliation audit trail storing every reconciliation action -- automatic matches, manual resolutions, and tolerance adjustments -- with the date, the operator's identity, and the matched records.

Settlement calculation computing the amount payable to each merchant or seller from their collected transactions in the settlement period, with platform fees, refunds, chargebacks, and reserves deducted before the net settlement amount is calculated. Settlement frequency configuration allowing different settlement schedules for different merchant tiers or agreement types -- daily, weekly, or monthly settlement, with instant payout available as an option for merchants above a performance threshold. Settlement statement production showing each merchant the transactions included in the settlement, the fees deducted, and the net amount paid, with the statement available in the merchant portal and delivered by email at each settlement date. Reserve management holding a percentage of the merchant's transaction volume in reserve for a configured period to cover chargebacks and refunds, with the reserve balance tracked per merchant and released automatically when the hold period expires. Chargeback management processing incoming chargeback notifications from the payment gateway, deducting the chargeback amount and the chargeback fee from the merchant's next settlement, and providing the merchant with the information needed to respond to the dispute through the gateway.

Velocity controls limiting the number and value of transactions from a single card, account, or device within a configured time window, with transactions above the limit declined or flagged for review rather than processed. Rule-based fraud screening applying configurable rules to each incoming transaction -- block-listed cards, block-listed email domains, high-risk IP geographies, unusual transaction patterns -- with matching transactions declined or routed to a manual review queue. Integration with third-party fraud prevention providers -- Sift, Kount, or similar -- passing transaction data to the provider's model and applying the risk score to the transaction routing decision. Device fingerprinting and behavioural signals from the checkout session passed to the fraud model alongside the transaction data to improve the accuracy of the risk assessment for card-not-present transactions. Fraud case management for transactions flagged for review, with a review queue showing the transaction details, the fraud signals that triggered the flag, and the action options -- approve, decline, or request additional verification -- with the decision recorded against the transaction.

Subscription plan management defining the billing cycle, the price, the currency, and the trial period for each product plan, with the plan linked to the customer's account at the point of subscription. Recurring billing engine processing subscription renewals automatically on the billing date, handling the payment attempt, recording the outcome, and triggering the next billing cycle or the dunning sequence depending on the result. Dunning management for failed subscription payments, executing a retry sequence over the configured number of days with the retry timing and communication to the subscriber configured per plan. Plan upgrade and downgrade handling the change in subscription plan mid-cycle -- the proration calculation for the remaining days on the current plan, the charge or credit applied to the next billing date, and the plan record updated to reflect the change. Subscription lifecycle events -- trial start, trial end, renewal, payment failure, cancellation -- published to a webhook or event stream for the downstream systems that depend on subscription status.