USPS Mailing Guidelines for Address Labels and Mailpieces

Correct address formatting and label placement help USPS equipment read and route a mailpiece. Use this guide as a practical checklist, then confirm the latest requirements in the USPS Domestic Mail Manual before a large or unusual mailing.

Quick answer: Put a complete, readable delivery address on the postage side. Check the finished mailpiece’s dimensions and thickness, then choose address-label stock or a paid shipping-label format to match your mailing.

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USPS mailing checklist

• Put the complete, legible delivery address on the same side as the postage.
• For letter-size mail, orient the delivery address parallel to the longer edge.
• Use dark ink on a light, plain background with a simple, easy-to-read font.
• Left-align the address block and keep logos, slogans and other text out of the address area.
• Verify the ZIP Code or ZIP+4 with the USPS ZIP Code Lookup.
• Check the finished mailpiece's dimensions, weight, thickness, flexibility and postage before mailing.

How to format a delivery address

USPS Publication 28 recommends a complete address with the recipient, delivery address, city, two-letter state abbreviation and ZIP Code. A secondary unit such as an apartment or suite should appear on the delivery-address line when possible or on the line immediately above it.

Use at least one space between the city, state and ZIP Code; USPS prefers two spaces between the state abbreviation and ZIP+4 Code. Directionals such as N, S, E and W and approved suffix abbreviations are part of the address and should not be omitted. See USPS Publication 28 for complete postal addressing standards.

Address-label placement and readability

USPS requires a clear space for the address, postage and other postal markings. On a letter-size piece, the recommended delivery-address location is the optical character reader area: at least 1/2 inch from the left and right edges, between 5/8 inch and 2 3/4 inches from the bottom edge.

• Apply the label straight, flat and completely adhered, with no curled corners.
• Do not wrap the address label around an edge or place it over a seam, closure or uneven surface.
• Keep every address line visible; window envelopes should maintain clearance around the complete address as contents shift.
• Place the return address in the upper-left portion of the side bearing postage. A return address is required for some classes and services.
• On clear or glossy labels, make sure the printed address remains dark, sharp and easy to read against the package. Test for smearing before mailing.

For USPS placement details, review DMM 102: Elements on the Face of a Mailpiece and the USPS Quick Service Guide 602.

Current size and shape standards

The finished mailpiece—not the label by itself—determines its USPS processing category and postage. These common retail standards were reviewed in October 2026:

First-Class Mail letter-size pieces over 3.5 ounces pay flat-size prices. Flat-size pieces that fail the flexibility or uniform-thickness standards are treated as parcels. Pieces outside these limits may be priced or processed in another category. Consult DMM 101: Retail Mail Physical Standards for exceptions and complete requirements.

Postcard labels: For cards claimed at retail card prices, choose paper label attachments with permanent adhesive and adhere them completely. Check DMM 101, sections 6.2.5 and 6.2.6 before using film labels or other attachments. Commercial card standards can differ from the retail dimensions shown above.

What can make a letter nonmachinable?

A letter may receive a nonmachinable surcharge or move to another processing category when it cannot travel through automated equipment. Common issues include:

• A square or unusually narrow shape with an aspect ratio below 1.3 or above 2.5.
• Clasps, strings, buttons or similar closures.
• Rigid construction or uneven contents such as loose keys, coins or pens.
• An exterior made of plastic or another nonpaper material. A window in a paper envelope alone does not make the piece nonmachinable.
• Thickness below 0.009 inch when the letter is more than 6 inches long or 4 1/4 inches high.
• A delivery address printed parallel to the shorter edge.

Rules vary by mail class and design. Commercial mailers should also review DMM 201: Commercial Mail Physical Standards or ask a USPS Mailpiece Design Analyst about an unusual piece.

Address Labels vs Paid USPS Shipping Labels

An address label identifies where mail should go; printing an address does not pay postage. A paid shipping label from Click-N-Ship includes postage and service information. Use the print format supplied by the service rather than shrinking it onto a small address label.

• For package labels, keep the whole label on one side and away from edges; do not fold or overlap it.
• Keep barcodes and the Postal Use area uncovered by tape. If a label contains an error, follow the service’s correction or refund process rather than altering it by hand.
• For ordinary address-only printing, choose label stock large enough for a complete, readable address.

See USPS Click-N-Ship printing guidance and our Click-N-Ship label sheet guide for printing help.

Choose and test your mailing labels

Use a label large enough for the full address without crowding. Our 2.625 x 1 inch address label sheets fit many envelope-addressing projects, while 4 x 2 inch address label sheets provide more room for packages and longer addresses. Download the matching layout from our free label templates.

1. Print one test sheet at 100% scale unless the template says otherwise.
2. Confirm that the address is sharp, complete and centered within each label.
3. Let the ink or toner set, then rub-test the print for smearing.
4. Apply one label to the actual envelope or package and check adhesion, contrast and placement.
5. Weigh and measure the completed mailpiece, then use the USPS Retail Postage Price Calculator for current postage.

Reviewed October 21, 2026. USPS standards and prices can change; the current Domestic Mail Manual and USPS postage calculator control.

Frequently asked questions

Where should I place an address label on a letter?

Place the complete delivery address on the side bearing postage and orient it parallel to the letter's longer edge. USPS recommends the OCR read area: at least 1/2 inch from the left and right edges, between 5/8 inch and 2 3/4 inches from the bottom.

Does a USPS address have to be in all capital letters?

USPS Publication 28 prefers uppercase letters but accepts lowercase type that meets postal OCR-readability guidelines. Use a complete, legible address with a uniform left margin and follow the requirements for the rate you are claiming.

What makes a letter nonmachinable?

Examples include an aspect ratio outside 1.3 to 2.5, rigid or uneven contents, clasps or strings, a nonpaper exterior, insufficient thickness for a larger letter, or an address parallel to the shorter edge.

Can I use clear or glossy address labels?

On letters and packages, check contrast, readability, adhesion and the requirements for the mail service. Clear film over a dark surface can make the address hard to read. For postcards claimed at retail card prices, USPS permits paper label attachments; do not assume clear film labels qualify.

How do I check the correct postage?

Weigh and measure the finished mailpiece, identify its shape and service, and use the current USPS Retail Postage Price Calculator. Avoid relying on an older fixed price because USPS rates can change.

How thick does a larger letter need to be?

If a letter is more than 6 inches long or 4 1/4 inches high, it must be at least 0.009 inch thick to avoid the thickness-related nonmachinable surcharge. Check the entire mailpiece against the other USPS letter standards too.

Can I shrink a paid shipping label to fit an address label?

Use the format and print settings supplied by the postage service. Do not shrink or alter a paid label to fit small address stock, cover its barcode with tape, or fold it over a package edge. An address-only label does not pay postage.

Choose Labels for Your Mailing

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