Gate2Shop is a payment gateway module in WHMCS.
GoCardless automates electronic direct debit payments.
iDeal via Mollie is a payment gateway in WHMCS.
The inpay payment gateway module is available in WHMCS.
The IP.Pay payment gateway module is available in WHMCS.
LinkPoint (First Data Global Gateway) was a payment gateway in WHMCS.
Use Mail In Payment to enter client payment details that display on the invoice.