Can you cover a US postal stamp with scotch tape?

NO, you should NOT use tape over a postage stamp, because the tape can invalidate the postage and the mail would more than likely be returned to the sender. Here's what the U.S. Post Office says: , you should "Affix your stamps securely, but do not put tape over the stamp(s) — this invalidates the postage."

Just try using a glue-stick or glue to secure a stamp to an envelope.

If the post office allowed tape to cover stamps, you could just keep reusing stamps because the postmark would only be on the tape (not the stamp itself).

If you need new stamps,you can buy stamps online at Stamps.com

No, it is not acceptable to use tape to affix stamps unless barely attached to the edges. The stamp must be fully cancelable with nothing impeding the cancel.

No. Being that I work for the USPS, it is not allowed to "scotch tape" a stamp on an envelope or small package because it will look like stollen postage and appear suspicious. If you have a stamp that just wont stick, do NOT glue, staple, or tape it to the envelope lol! Just go to the post office and they should be able to replace the stamp for you. :)

Going to the post office and getting a replacement stamp is not an option. You'd think they'd do that, but no. I've been told repeatedly they won't (Schaumburg, Illinois).

So I use tape and hope for the best. Tape the underside of the stamp really tightly

you can weld them on, or just put a nail in the corners, either of these methods will attach your stamp. I prefer pop riveting them on. But this may cause jams in the machinery.welding them on is tricky and requires a steady hand.
When we were kids our mom used the gum stuck under our table to adhere the stamp to the envelope, we didn't have the 9 cents for a new stamp. we learned to adapt. Hope this works

Use an iron on low heat if it has any stickiness to it at all. Put some fabric between the envelope with the stamp affixed and put the fabric over it and iron it a little bit on top.