WHMCS Payment Gateway Module

This package builds a WHMCS payment gateway module for a provider WHMCS does not ship with, so your clients can pay invoices through it and WHMCS marks them paid only when the provider confirms the payment. It suits businesses using a regional card processor, a bank transfer API, a crypto processor such as NOWPayments or a local wallet.

The callback is the part that matters

Most broken gateway modules fail at the callback, not at checkout. Mine sit in modules/gateways/callback and do four things before any payment is recorded: verify the provider's signature, confirm the invoice exists with checkCbInvoiceID, compare the amount and currency with the invoice, and reject a transaction ID already on record with checkCbTransID. Only then does addInvoicePayment run, and every callback, accepted or refused, is written to the gateway log.

How far each plan goes

• Starter: a redirect or hosted checkout, signed callbacks, the duplicate check and a test mode switch.
• Business: refunds from the WHMCS admin, gateway fees recorded against the payment, multi-currency handling and a payment status page for the client, all tested in the provider's sandbox.
• Premium: a stored payment method so WHMCS can charge renewals automatically, recurring payments where the provider supports them, partial payments with overpayment credited, retry handling for repeated webhooks and a reconciliation report.

Card data and approval

I build gateways around hosted pages, hosted fields or tokens, so card numbers never pass through your WHMCS server, which keeps your PCI scope small. Your merchant account, its fees and its approval belong to the provider and you; I start once you have sandbox credentials and a live account is underway. For a broader view of gateway work, see the payment gateway integration page.