What Triggers Extra Postage on Invitations
Extra postage comes from two separate places. One is weight: each ounce past the first adds$0.29. The other is the nonmachinable surcharge: a flat $0.49 per piece when the envelope cannot go through the sorting machines.
The surcharge is charged once, however many reasons apply. A square envelope with a wax seal and a ribbon pays the same$0.49 as a square envelope with nothing on it. That makes the choice simple: avoid every trigger, or accept the surcharge and use as many as you like.
Triggers, one by one
- Wax sealsA raised seal makes the envelope uneven, which the sorting machines cannot handle.
- Ribbon, twine and bowsTies on the outside count as string closures; knots inside make a lump.
- Square envelopesEvery square fails the aspect ratio rule, whatever it weighs.
- Rigid invitationsAcrylic, wood and thick board do not bend around the sorting belt.
- Vellum wraps and pocket foldsThese rarely trigger a surcharge by themselves, but they add weight fast.
- Heavy invitationsEvery ounce is a price step, and past 3.5 oz the large envelope price applies.
Postage by weight
- 1 oz invitationWhat it costs and which stamps cover it
- 2 oz invitationWhat it costs and which stamps cover it
- 3 oz invitationWhat it costs and which stamps cover it
The full list USPS uses
A letter is nonmachinable if any one of these is true:
- Its length divided by its height is under 1.3 or over 2.5. Every square fails this.
- The address runs along the shorter side.
- It has a clasp, string, button or similar closure.
- Something inside or on it makes the thickness uneven.
- It is too rigid to bend easily.
- It is wrapped in plastic, or the outside is not paper.
- It is larger than 4 1/4 x 6 in but thinner than 0.009 in.
The list comes from theUSPS Domestic Mail Manual, section 101.1.2. To see which ones apply to your invitation, run it through the calculator, or readhow to avoid the surcharge and postage by envelope size.