Payment Processing Software Development

Payment gateway integration connecting to Stripe, Adyen, Braintree, Worldpay, or direct acquirers through their APIs, with card, bank transfer, digital wallet, and local payment methods configured per gateway and per market. Multi-gateway routing directs payment transactions to the optimal gateway based on payment method, transaction currency, issuer country, or merchant category, with fallback routing to a secondary gateway when the primary is unavailable. Gateway-agnostic transaction management maintains a unified transaction record regardless of which gateway processed the payment, so reporting, reconciliation, and customer service queries don't require identifying which gateway handled each transaction. Idempotency handling ensures 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 consumes payment status events from each gateway and updates the transaction record and downstream systems in real time rather than through polling.

Multi-currency transaction processing accepts payments in the customer's local currency and settles to the merchant in their preferred settlement currency, with FX conversion applied at the point of settlement using the exchange rate source and margin configured for the product. Real-time FX rate integration pulls rates from a currency data provider or from the payment gateway's FX service, with the rate applied to each transaction recorded for audit and customer disclosure where the product requires it. A multi-currency ledger maintains separate currency balances for each account or merchant, GBP, EUR, and USD balances tracked separately without currency blending. FX settlement calculation produces 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 shows 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. An exception queue presents unmatched or partially matched items to the reconciliation team for manual review. Each exception shows 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. A daily reconciliation report shows the reconciled and unreconciled positions across all payment methods and currencies, produced automatically at the configured time each day. Tolerance handling automatically marks low-value discrepancies, typically caused by FX rounding, as reconciled within tolerance rather than adding them to the exception queue. A historical reconciliation audit trail stores every reconciliation action with the date, the operator's identity, and the matched records.

Settlement calculation computes 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 allows different settlement schedules for different merchant tiers or agreement types, daily, weekly, or monthly, with instant payout available for merchants above a performance threshold. Settlement statement production shows 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 holds 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 processes incoming chargeback notifications from the payment gateway, deducts the chargeback amount and fee from the merchant's next settlement, and provides the merchant with the information needed to respond to the dispute.

Velocity controls limit 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 applies 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, passes transaction data to the provider's model and applies the risk score to the transaction routing decision. Device fingerprinting and behavioural signals from the checkout session are passed to the fraud model alongside transaction data to improve risk assessment accuracy for card-not-present transactions. Fraud case management for transactions flagged for review presents 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 defines the billing cycle, price, currency, and trial period for each product plan, with the plan linked to the customer's account at the point of subscription. A recurring billing engine processes subscription renewals automatically on the billing date, handles the payment attempt, records the outcome, and triggers the next billing cycle or the dunning sequence depending on the result. Dunning management for failed subscription payments executes a retry sequence over the configured number of days, with retry timing and communication to the subscriber configured per plan. Plan upgrade and downgrade handling manages 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, are published to a webhook or event stream for the downstream systems that depend on subscription status.