Do you know our module Paypal No fees ? Well this is the opposite. You give a discount (or add credit) if your customers selects one gateway you prefered.
Installation: Edit the invoiceAddCredit.php file and then upload it into your WHMCS’s hooks directory (/includes/hooks/).
A) Edit $percent to set the percentage of the total invoice to be added as a credit to the account (15% is default).
B) Edit $payproc to set the payment processor you want to issue the credit on their account (bitpay is default, if unsure what it’s called check the tblinvoices table in the database for the exact name).
C) Edit $desc to set the description that appears in the credit to whatever you’d like.
D) Edit $adminuser to set the admin user that the credit is issued under (make sure it’s valid in WHMCS since this is required).
A) Edit $minpay if you want to set a minimum invoice total required before a credit is added (this can by helpful to filter by billing cycle, default is 0.00).