A Direct Debit Authority needs to be created in order for a Bank Account to be used as a funding source (Direct Debit/ACH).
The Direct Debit Authority is an authorization from the User to debit their Bank Account for the Item amount or for the funding of a Wallet Account. Ensure that you actually obtain this authorisation because in the event of an issue, it will be required as proof of authorization.
You will need to provide them with a link and checkbox to the Assembly direct debit agreement.