A quick handoff matters. Deliver the final file, obtain written acceptance, and attach the invoice in the same thread. Reference the approved deliverable and next step. This preserves momentum and gives approvers everything required in one place, while goodwill is strong and context still alive.
Ask when accounts payable processes invoices, which days they batch payments, and which formats pass validation fastest. Then mirror that schedule. If their bank runs ACH on Wednesdays, submitting Tuesday afternoon shortens lag. Respecting internal rhythms turns you into an easy vendor, and easy vendors get paid first.