WHMCS accepts a wide variety of payment gateways. Among the most well-known are:
Stripe: Accepts credit cards and other payment methods.
PayPal: PayPal Standard and PayPal Express Checkout are both supported.
Authorize.Net: Allows credit card payments and electronic checks.
2Checkout: Accepts payments via a variety of options, including credit cards and PayPal.
Skrill: Accepts and processes online payments and transactions.
Square: Accepts credit cards and offers a complete payment solution.
Worldpay: Allows for both online and in-person payments.
BitPay: A Bitcoin payment service.
CoinGate: Accepts a variety of coins as payment.
Braintree: A PayPal-owned company that provides a scalable payment solution.