We removed this in WHMCS 8.8.

SlimPay is a Direct Debit payment gateway supporting both BACS Direct Debit for UK-based customers and SEPA for EU-based customers. Direct Debit is a pull-based bank-to-bank payment method: a customer authorizes a merchant to automatically debit their bank account for the amount of the subscription.

Direct debit is not an instant payment service. Payment processing may require multiple days.


Supported Features

Type: Third-Party

3D SecureRemote Update CardRemote Delete CardAddPayMethod API

Adding the SlimPay Payment Gateway

To set up the SlimPay payment gateway in WHMCS:

  1. Go to Configuration () > Apps & Integrations or Addons > Apps & Integrations.
  2. Click SlimPay.
  3. Check Show on Order Form to display this payment method in the Client Area during checkout.
  4. Enter your SlimPay credentials.
  5. Click Save Changes.
  6. In SlimPay, set the return URL to, where is the URL to your WHMCS installation.

Test Mode

You can use test mode to simulate payment processing without actually causing a transaction to occur. This can be useful for testing your configuration.

Instant Activation for New Orders

Direct debit is not an instant payment service. Payments can take up to a few days to clear and fully complete processing.

To provision new orders immediately on the completion of a mandate agreement and initiation of payment, check Instant Activation for New Orders. The system will mark the invoice as paid and will perform any successful payment automation actions immediately.

Supported Currencies

SlimPay supports payments in Euro and British Pounds. The module will automatically select the appropriate BACS or SEPA payment method based on the currency of the invoice.

Payment Workflow

The first time a user pays an invoice using the SlimPay payment gateway, they complete a mandate that authorizes you (the merchant) to debit their bank account automatically each subscription cycle.

  • The customer only has to do this once.
  • A Your mandate has been signed message will display when the customer completes the mandate.

After creation of a mandate for the first time, the system will initiate a payment request. Until the payment has fully completed, the invoice will display a Payment Pending status and display a message to the user. No automated provisioning actions will occur until the payment has fully cleared unless you enable Instant Activation for New Orders.

For recurring invoices where a mandate agreement already exists between you and the customer, WHMCS will automatically request a payment capture on the due date of the invoice.

Rejected Payments

The SEPA scheme allows an eight week period during which the payee can reject or reverse the payment. WHMCS will monitor for any changes in the payment status of invoices with SlimPay during this time and will automatically process them.

For more information, see Payment Reversals.



Last modified: June 11, 2024