For selecting the mandate at contact level:

#. Go to *Invoicing > Customers > Customers*.
#. Open or create one contact that has a parent.
#. On the "..." page, fill *Contact Mandate*.
#. That mandate will be populated in the debit order.

Then the normal flow will be:

#. Go to Invoicing > Customers > Customer invoices.
#. Create a new invoice for that contact.
#. Post the invoice.
#. Add it to a payment order, by any of the options that you can check on the *account_payment_order* module.
#. The populated mandate will be the one on the contact.
