Currently there is no way to retrieve via the API whether a direct debit has been requested via GoCardless for an invoice.
This information is only available when viewing the invoice online as a team member.
Ideally we would want the GoCardlessBillID returned in the Invoice_Get response and also another API method DirectDebit_Get which returns the information found in the Direct Debit report:
- Bill ID
- Created
- Collect Date
- Status
- Amount