Set up a BACS Direct Debit mandate via GoCardless and handle the submission timing windows

Steps

1. Create a customer and a bank account via the GoCardless API, then create a mandate linking the bank account to your creditor — GoCardless handles submission to Bacs on your behalf.
2. Note that BACS mandates require a processing lead time: new mandates must be submitted to Bacs 3 business days before the first debit (the AUDDIS submission cycle).
3. After mandate creation, it will enter 'pending_submission' then 'submitted' then 'active' states; do not create a payment until the mandate is 'active'.
4. Create a payment by specifying the mandate ID, amount, and charge_date — the charge_date must be at least 2 business days in the future to allow Bacs processing.
5. Listen for GoCardless webhook events on mandate and payment resources: handle 'mandate_cancelled', 'payment_failed' (with failure reason), and 'payment_paid_out'.
6. For recurring charges, use GoCardless subscriptions (a higher-level object) which automatically schedule payments and handle retries within Bacs rules.