Set up a GoCardless bank debit mandate and collect a payment via ACH, SEPA, or BACS

Steps

1. Create a Customer and CustomerBankAccount, or use a Redirect Flow (POST /redirect_flows) to collect bank details from the customer via GoCardless's hosted page — this is the recommended approach as it handles local mandate language (SEPA mandate, BACS DDI, ACH authorization).
2. Complete the redirect flow after the customer returns: POST /redirect_flows/{id}/actions/complete with 'session_token'; the response contains a Mandate ID.
3. Verify the mandate status by listening for the 'mandates.active' webhook event — do not attempt to collect payments against a mandate in 'pending_submission' state.
4. Create a Payment against the active mandate: POST /payments with 'amount' in minor units, 'currency', 'links.mandate', and 'charge_date' (optional; defaults to the earliest possible collection date respecting the scheme's notice period).
5. Listen for webhook events on the payment: 'payments.submitted' (sent to bank), 'payments.paid_out' (funds received by you), 'payments.failed' (bank rejection), and 'payments.charged_back' (customer dispute).
6. For failed payments, check 'cause' on the event to distinguish insufficient funds (can retry after notice period) from mandate cancelled (must re-authorise the customer).