What is a folded self-mailer?
A folded self-mailer (FSM) is a letter-size piece formed by folding a single sheet. It is not enveloped, not bound, and has no staples. It must be sealed closed with tabs (wafer seals) or fugitive glue to qualify for letter-rate postage and to survive USPS high-speed processing without jamming. This sealing requirement is a letter-size rule; a piece folded to flat size is a flat, not an FSM, and does not use these tabs (see Does a sheet folded to a flat size need tabs).
A tri-fold is a sheet folded twice, producing three panels. A bi-fold is folded once, producing two panels. A quarter-fold is folded twice at right angles.
What size can a folded self-mailer be?
Folded (final) dimensions must fall within:
- Length: minimum 5 inches, maximum 10.5 inches
- Height: minimum 3.5 inches, maximum 6 inches
- Aspect ratio (length divided by height): between 1.3 and 2.5
- Thickness: minimum 0.007 inches, or 0.009 inches if the piece exceeds 4.25 inches in height or 6 inches in length
Note: the folded self-mailer maximum (10.5 x 6) is smaller than the general letter maximum (11.5 x 6.125). A piece can be letter-size yet still exceed the folded self-mailer envelope, which changes how it must be handled.
Does a sheet folded to a flat size need tabs?
The tabbing and sealing rules in this file apply ONLY to letter-size folded self-mailers. Tabbing is a letter-size processing requirement (DMM 201.3.11 through 201.3.17); flats are not tabbed this way.
If a sheet is folded to finished dimensions that exceed letter size (more than 6.125 inches high or more than 11.5 inches long), the piece is a flat, not a folded self-mailer, and it does NOT need the self-mailer tabs. Flats are prepared under flat standards, not the letter tabbing rules here.
Worked example: an 11 x 17 sheet folded in half to 8.5 x 11 is 8.5 inches high, which exceeds the 6.125-inch letter height, so it mails as a flat (see What size is a flat) and does not require a tab. Only when a piece is folded down to letter size (for example an 11 x 17 quarter-folded to about 5.5 x 8.5) do the self-mailer tabbing rules in How many tabs does a folded self-mailer need and How many tabs does a quarter-fold need apply.
Does an 8.5 x 11 tri-fold need tabs?
An 8.5 x 11 sheet tri-folded (letter fold) produces a finished piece of about 8.5 x 3.67 inches. That is within the folded self-mailer size limits, so it is a valid folded self-mailer and it does require tabbing. See How many tabs does a folded self-mailer need for the number of tabs and Which panel does the address go on for panel placement.
How many tabs does a folded self-mailer need?
Applies to LETTER-SIZE folded self-mailers only. A sheet folded to a finished size larger than letter is a flat and is not tabbed this way; see Does a sheet folded to a flat size need tabs.
For basic bi-fold and tri-fold self-mailers, tabs must be non-perforated and placed on the top edge:
- Up to 1 ounce: two tabs, 1 inch in diameter, on 70 lb book stock
- Over 1 ounce up to 3 ounces: two tabs, 1.5 inch in diameter, on 80 lb stock
Placement options for bi-fold and tri-fold, each tab within 1 inch of the corners:
- Two tabs on the top edge, one near each corner, OR
- One tab on the leading edge and one on the trailing edge, each within 1 inch of the top
No tabs are allowed on the bottom edge of a self-mailer.
How many tabs does a quarter-fold need?
Quarter-fold pieces need more tabs than bi/tri-folds:
- Up to 1 ounce: two tabs (same top-edge placement as bi/tri-fold)
- Over 1 ounce up to 3 ounces: three tabs, one on the leading edge and one on the trailing edge within 1 inch of the top, plus a third on the lower leading edge, 0.5 inch from the bottom
Which way should the final fold face?
Applies to LETTER-SIZE folded self-mailers only (see Does a sheet folded to a flat size need tabs).
- The final fold cannot be on the top. It must be on the bottom, or in the case of oblong pieces on the leading (right) edge.
- Tri-fold: fold from bottom to top so the final folded panel forms the non-address side.
- Oblong self-mailers must have the final fold on the leading right edge.
Which panel does the address go on?
Applies to LETTER-SIZE folded self-mailers. Flats place the address in the top half of the piece instead; see Where does the address go on a flat.
For tri-folded self-mailers, the mailing address must be on the middle panel, the center panel with fold creases on both its top and bottom edges. The final fold creates the non-address side of the piece.
What paper weight does a self-mailer need?
- 1 ounce or less: at least 70 lb book (text/offset) stock
- Over 1 ounce up to 3 ounces: at least 80 lb stock
- Maximum weight for a folded self-mailer: 3 ounces
Can I use fugitive glue instead of tabs?
Applies to LETTER-SIZE folded self-mailers only (see Does a sheet folded to a flat size need tabs).
Fugitive glue may be used instead of tabs to anchor the piece and inserts. If the bottom of the piece is open, inserts must be anchored in place with fugitive glue. Perforated tabs are not permitted under any configuration.
Why this matters commercially
Proper tabbing and folding qualify a self-mailer for letter-rate automation postage instead of the higher flat rate. On a large campaign the per-piece difference is substantial, so getting the tab count and placement right is a cost decision, not just a compliance one. When a customer's design cannot meet these rules, route them to a Plavidian rep rather than guessing.