What Bulk and Periodical Mailers Need to Know about the New USPS "Flat Tray" Rule

Scott HochbergScott Hochberg
 Postage $aver Software


Effective January 22, 2023, USPS has changed the way "flats" are prepared for Marketing Mail (bulk mail) and Periodical Class mail rates. Mailers are required to use "flat trays" (also called "tubs") instead of sacks to submit flats.

USPS tub (flat tray)This is a "flat tray". (Yes, I know it's not flat. But it's used for flats. The flatter trays that you use for letter-sized mail are called "letter trays.")

Previously, Marketing Mail mailers have been required to use sacks (or, in some case, letter trays) for flats. Periodical Class mailers have had the option of preparing sacks using either flat trays or sacks, but are no longer allowed to use sacks. (There are some exceptions and a short grace period ... see below.)

Three important warnings:

What are flats?

Postage Saver software makes postal bulk mailing easy If you have been using sacks to send your Marketing Mail or Periodical Class mail, and the mail is not a parcel, then it is a flat.

A flat is any mail that is rectangular, flexible, and fits at least one of the following requirements, regardless of whether it is a card, envelope, or package: A flat also cannot be "lumpy". In other words, its thickness may not vary more than 1/4" except within 1" of the edges.

* Every Door Direct Mail flats have a different minimum length, but EDDM is not part of this rule change.

How to arrange your mail in a flat tray:

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How do I create "columns" if bundling causes my pieces to roll up?

You're not really supposed to have rolled bundles, and that's especially important when using flat trays. Bundles are supposed to lie flat. If the rubber band tension causes the pieces to roll up, use rubber bands that won't do that. Here's what USPS says about bundling flats: For Periodicals, no bundling is required or allowed for a particular tray if all of the bundles in that tray have the same destination and sort level as the tray itself.

For example, if the tray tag says it's a 3D tray going to 770, and the endorsement line on all of the pieces says 3D 770, then no bundles are used. But if the endorsement lines in one of the bundles in that tray say 5D 77005, then all pieces in the tray must be bundled.

For each tray, Postage $aver figures out whether bundles are used, and shows that on the Mail Preparation Instructions report.


Exceptions to the flat trays rule, and grace period:

USPS has provided the following exceptions to the flat tray rule where sacks are still permitted.

For Periodical Class, sacks can still be used for flats when presorted at the following levels: Note that the Periodical Class per-container charge for sacks is more than the charge for the same mail if prepared in flat trays.

For Marketing Mail, sacks can still be used for flats when presorted at the following levels: Temporary grace period: USPS has announced a grace period for the new flat tray requirements, through February 21, 2023. Per USPS:

"This grace period is to allow the mailers time to modify their operations, adjust their mailing plans, and any other procedures to accommodate this change. It will also allow for receipt of mail already in transit for drop ship at the time of the implementation.

During the grace period, the Postal Service will continue to accept and process this flat volume in sacks, bundles, or flat trays without penalty or assessment. The grace period will expire February 21, 2023. At that time, mailers will be required to be in compliance with the new rules. Mailers are able and encouraged to adopt the new rules as soon as they ready."


New Instruction from USPS - released and then clarified 1/20/23: Mailers who submit electronic documentation using mail.dat or mail.xml files, and who require an extension for use of sacks after January 22, 2023, must complete the spreadsheet posted here. Mailers must complete the Sack Extension Request sheet each week and submit it to PCSC@usps.gov each Friday by 11:59 pm EST with the list of that week's impacted mailings. Here are details on how to modify mail.dat and mail.xml files if you are using the grace period.

Mailers who use the USPS Postal Wizard or paper postage statements will have any necessary postage adjustments made by the Bulk Mail Entry Unit when they submit their mailings, and should not complete the spreadsheet mentioned above.

Because some of the exceptions and the grace period were not announced until early January, shortly before our software revisions were scheduled to be released, Postage $aver Pro and Lite will not support the exceptions or the grace period. The update for the January 22 USPS price increase is based on all Marketing Mail flats and Periodical Class flats being prepared in flat trays, as was originally announced by USPS.
Postage Saver software makes postal bulk mailing easy

The flat trays rule means higher postage for some nonbarcoded flats:

USPS has changed the minimum number of pieces to earn various pricing levels when preparing Marketing Mail nonbarcoded flats.

Marketing Mail flats are priced based partly on the sort level of the pieces. For nonbarcoded Marketing Mail flats, that means, for example, that a sack of pieces all going to the same 5-digit zip gets a better rate than a sack of pieces just going to the same 3-digit area, ADC area, or mixed. For sacks, the minimum to qualify for its own sack has been 125 pieces or 15 pounds, whichever is lower.

The new USPS rule sets a different minimum for nonbarcoded pieces in flat trays. To qualify for its own tray, a sort level now needs to "fill" the tray, which means it has enough pieces to make an 8" stack.

Some quick math works out that for any piece thinner than 1/16", more than 125 pieces is now necessary to earn the lower rates. For a large card printed on 16 point stock, for example, you would need 500 pieces to one zip (or zip scheme) to get the 5-digit price. If your whole mailing was less than 500 pieces, you'd go from paying 65.3 cents per piece to 92.3 cents per piece!

This change in minimums only applies to Marketing Mail nonbarcoded flats. Marketing Mail barcoded flats are priced based on the sort level of the bundle they are in, not by the sack or tray level. Since bundle sizes are not changing, those rates are calculated just as they have been.

We have asked USPS to look at whether the effect of the change on pricing was intended, and to reconsider, but for now, the rule remains in effect.

Questions? Ask us and we'll do our best to answer.

Scott Hochberg
Scott Hochberg started Postage Saver Software in 1994. He's been helping small businesses and nonprofits save postage with postal bulk mail for more than 25 years. Scott's based in Austin, Texas. He's happy to answer your bulk mailing questions!