I've finished stuffing and putting a single "Forever" stamp on my Save the Dates. After some Googling on how to mail these in at the post office (for hand-cancelling), I just read that the extra "bump" from the bow in my Save the Date is going to cost an extra 20 cents (non-machinable surcharge). This surcharge was of 4/2021. I would hate to waste extra Forever Stamps so should I just head to the Post Office with one of the invitations to purchase extra regular stamps to make up for the bump or will they just let me pay for them using my card without affixing additional stamps on each envelope? I wish I had known about this non-machinable surcharge or I would have never added the bow.