USPS Media Mail Incidental Enclosures: Notes, Invoices, and Limits

A Media Mail package can include more than just the book, disc, or score you’re shipping, but the extras are tightly limited. You can add a short personal note or dedication, an invoice or bill for the items inside, brief handling and identification markings, a small closely related First-Class enclosure, and certain qualifying printed matter. What you cannot include in a Media Mail package is anything that reads like a personal letter, any general merchandise, or advertising outside a narrow book-announcement exception. Get it wrong and USPS can open the package, reclassify it, and charge the postage difference to you or your recipient.

The Primary Contents Have to Qualify First

Everything below assumes the package itself is eligible for Media Mail. That means the dominant contents are books of at least 8 pages, sound or video recordings, printed music, playscripts and manuscripts, 16mm or narrower film, printed educational tests, educational reference charts, medical loose-leaf pages for professionals and students, or computer-readable media with guides prepared solely for use with that media.¹ Video games, comic books, clothing, and general merchandise do not qualify, and mixing them in with eligible items does not save the package.²

Notes, Dedications, and Other Writing You Can Add

The Domestic Mail Manual permits certain written additions on the media, its packaging, or an enclosure without triggering extra postage.³ These are meant to be brief and functional:

Sender and recipient names, occupations, and addresses preceded by “From” or “To,” along with handling directions.
Marks, numbers, names, or letters describing the contents.
Short greetings such as “Happy Birthday, Mother” or “Do Not Open Until Christmas.”
Instructions for using the item being mailed.
A handwritten dedication or inscription in a book, as long as it does not become personal correspondence.
Highlighting or annotations that call attention to passages in printed material.
Corrections to typographical errors, or manuscripts with related proof sheets.
Handling instructions such as “Do Not Bend” or “Fragile.”

The line that trips up most senders is the one between a “dedication” and a “letter.” Writing “To John — Merry Christmas, love Mom” inside the cover is fine. Folding a two-paragraph letter about your vacation between the pages is not, and it turns the whole package into a compliance problem. The rule turns on length and tone rather than a set word count, so keep any handwritten addition short and tied to the item or the occasion.

Invoices and Packing Slips

You can include an invoice or bill inside any Media Mail shipment, or attach it to the outside in an envelope marked “Invoice Enclosed,” provided it relates only to the items in that package.⁴ The invoice may show:

Names and addresses of sender and recipient.
Descriptions and quantities of the items, including price, tax, style, stock number, size, and quality.
Order or file number, order date, shipment date, shipping method, weight, postage paid, and the packer’s name or initials.

What the invoice cannot do is double as a marketing piece. You cannot use it to advertise other products, tuck in a catalog under the guise of a receipt, or promote future orders. Stick to the current shipment.

A Small First-Class Enclosure

The Domestic Mail Manual lets you include a piece of First-Class Mail inside a Media Mail package without paying First-Class postage on top. USPS calls this an “incidental First-Class Mail attachment or enclosure.”⁵ To qualify, the enclosure must be closely related to the main item, secondary to it, and not interfere with processing.

In practical terms, this covers a personal note or greeting tucked into a book, a bill for the product, or a statement of account for past purchases.⁴ Postage is calculated on the combined weight of the media and the enclosure. The catch is that the enclosure cannot be the real reason for the shipment. A paperback with a birthday card tucked inside qualifies; a birthday card with a paperback added as cover does not.

Book Announcements and Loose Printed Matter

Media Mail prohibits advertising in general, but publishers get a narrow exception. Books shipped at Media Mail rates may contain incidental announcements of other books, printed as book pages, with ordering conditions if needed.³ The announcements can only advertise other books, not bookmarks, reading accessories, or audiobook subscriptions. Up to three of those announcements may include one order form each, on top of the single standalone order form and one envelope or postcard that may be bound into the book.

Separate from that, any printed matter that would independently qualify as USPS Marketing Mail can ride along loose in the package, or be printed directly on the wrapper, envelope, tag, or label.⁴ So a publisher can include a printed flyer for upcoming titles without violating the advertising rule, as long as the flyer meets Marketing Mail standards on its own.

What You Cannot Include

Everything outside the categories above is off limits. The most common violations:

Personal letters. Anything longer or more conversational than the brief markings listed earlier is treated as correspondence and requires First-Class postage.
General merchandise. Clothing, toys, household goods, jewelry, or any non-media item added to a Media Mail package triggers reclassification.
Commercial advertising. Outside the book-announcement exception and qualifying Marketing Mail printed matter, ads are not allowed.²
Ineligible media. Video games, comic books, and digital storage devices that don’t contain prerecorded educational content don’t qualify, and pairing them with eligible items doesn’t fix the problem.

What Happens if USPS Opens the Package

Media Mail is not sealed against inspection. Paying the Media Mail rate is treated as consent for USPS to open the package and verify the contents are eligible.⁶ If an inspector finds ineligible items or personal correspondence that should have gone at a higher rate, the ineligible matter is reclassified at the proper rate. The package is either delivered with a “Postage Due” charge on your recipient, or the sender is contacted for the difference.¹ Inspections happen inconsistently from office to office, but the risk is always there, and shippers who routinely push the limits are more likely to attract scrutiny. If you receive a revenue deficiency notice and believe it’s wrong, you have 30 days to submit a written appeal to the official who issued it.⁷

1
United States Postal Service. Notice 121 – Media Mail Service
2
United States Postal Service. Media Mail Service – Technical Information
3
Postal Explorer. Domestic Mail Manual – Media Mail and Library Mail Prices and Eligibility
4
Postal Explorer. Media Mail and Library Mail Prices and Eligibility
5
Postal Explorer. Domestic Mail Manual 703 – Nonprofit USPS Marketing Mail and Other Unique Eligibility
6
USPS. What is Media Mail
7
Postal Explorer. Mailer Compliance and Appeals of Classification Decisions