Can I create an return envelope ( Stamp Addressed Envelope) and pay the postage with my Franking Machine?
Firstly, any franked mail must be sent on the same day. So franking mail in order to be sent out the following day is not allowed. This also means you can't frank an item that is being used as a return envelope. If you are enclosing return envelopes, they must either have a stamp or be prepaid.
Hope this helps