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Yes, you can use tape on an envelope, but keep it off the address, the stamp, and the bottom-right corner where postal machines print their routing barcode. Tape seals a flap fine, though glue works better for automated sorting. Never tape over the address or postage: it can confuse the scanners and, on the stamp, it looks like reuse.
| Do | Don't |
|---|---|
| Tape the flap shut when the adhesive is weak | Tape over the address block |
| Use a small piece of clear tape on a torn window, address still fully visible | Tape over the stamp or postage label |
| Reinforce the edges of a stuffed envelope | Cover the bottom-right corner where the routing barcode goes |
| Use decorative tape on the back of the envelope | Wrap the whole envelope like a package |
Three places are off limits. First, the address: automated scanners read the address block with cameras, and tape over it creates glare and distortion that can send your letter to manual handling or the wrong city. Second, the stamp: tape over postage interferes with cancellation, and worse, it looks like you're trying to reuse an uncancelled stamp, which is exactly what postal inspectors watch for. If your stamp won't stick, use a glue stick on its back, not tape over its face.
Third, the bottom-right corner of the address side. That's where sorting machines spray the routing barcode after reading the address, and tape there can prevent the barcode from sticking or being read. The same goes for the top-right corner around the stamp. The rule of thumb is simple: tape belongs on the flap and the seams, never on the front face where the machines do their reading.
Washi tape is fine in moderation. It's thin, light, and peels cleanly, so a strip on the flap or a decorative border on the back of the envelope won't bother anyone. What causes trouble is heavy packing tape wrapped around a letter envelope: it adds stiffness and uneven thickness, which is exactly what jams sorting machines. Save the packing tape for parcels and padded mailers, where it's expected.
The machine-friendly choice is still glue. A glue stick on a weak flap seals flat, adds no thickness, and never confuses a scanner. If you do use tape on the flap, press it down smooth and trim the ends; a lifted tape edge is what catches in equipment. And keep decorative tape away from the address side entirely. A pretty envelope that can't be read by the scanners gets hand-sorted, which is slower, and in December it can be a lot slower.
This is where the myth lives: that any tape on a window envelope gets it rejected. It doesn't. A small piece of clear tape over a torn cellophane window is usually fine as long as the address behind it stays fully visible and readable. Postal workers see patched windows regularly; it's not a reason to refuse the piece.
What does cause problems is heavy taping: multiple layers of opaque tape, tape that wrinkles the address, or tape that covers part of the address block. If the window is badly torn, the honest fix is a fresh envelope. Window envelopes are cheap, and reprinting or rewriting the address takes two minutes. A patched window that obscures even one line of the address can send the letter on a detour through manual sorting, which defeats the purpose of using a window envelope in the first place.
One more practical note: none of this matters if someone else mails the letter for you. When LetterAgent prints and mails a letter, the envelope is sealed and addressed at the print facility, so there's no flap to tape and no window to tear. You describe the letter to your AI assistant, approve the quoted price, and the finished, properly sealed envelope goes out without you touching tape at all.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is printed and mailed.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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