Preparing for the 2026 USPS Rate Case: The Elimination of Bundling in Tubs for Marketing Mail Flats

The United States Postal Service has announced its upcoming Market-Dominant Price Change, scheduled to take effect on July 12, 2026. While the rate case introduces several exciting new promotional discounts and expanded weight limits, it also brings important structural updates to mail preparation that will directly impact presort operations.

One of the most significant changes for direct marketers is the elimination of bundling for Marketing Mail Flats prepared in flat tubs.

If your organization frequently mails Marketing Mail Flats, here is a detailed breakdown of what is changing, why the USPS is implementing this rule, and how you can prepare your operations.

What is Changing?

Currently, mail preparation and presort options allow mailers to submit Marketing Mail Flats in bundle form when presenting them in flat tubs. Under the new 2026 rules, this will no longer be allowed.

To replace the bundle structure, the USPS is introducing a new 50-piece minimum requirement for these tubs. This minimum is designed to ensure that containers are utilized efficiently as they move through the postal network.

This structural adjustment shouldn't come as a total surprise to the industry, as it mirrors the exact same improvement the Postal Service successfully implemented for First-Class Mail Flats during last year’s rate case.

Why is the USPS Making This Change?

The primary goal of this update is to align the available presort options with current processing operations and to resolve a costly inconsistency.

Under the previous rules, a mailer could fill a "mixed" tub with 5-digit and 3-digit bundles. When this happens, the Postal Service has to incur the operational costs associated with sorting the mixed tub. However, the customer is able to claim the lower postage rate associated with the sortation of the bundle.

By eliminating bundles in tubs, the USPS ensures that the costs of processing the tub accurately align with the pricing of the tub’s contents.

How Will This Impact Pricing and Technology?

The good news for mailers is that these preparation changes are not accompanied by any changes to listed prices. The USPS has only adjusted the billing determinants to reflect the price impact associated with the new tub requirements.

However, there will be technical impacts for your mailing software. Both the Mail.dat and Mail.XML technical specifications and validations will be updated to reflect the elimination of bundles in tubs.

Next Steps for Mailers

With the July 12, 2026 implementation date approaching, now is the time to review your presort strategies. You should plan to meet with your mail preparation teams and your mailing software vendors to ensure that your systems will be updated to handle the new validations. By transitioning away from bundles and preparing for the new 50-piece tub minimum, you can ensure a seamless experience for your Marketing Mail campaigns when the new rules take effect.