A business address format puts the recipient’s name, the company, the street address with any unit designator, and the city, state, and ZIP Code on four left-aligned lines, in that order, in uppercase, with no punctuation except the hyphen in a ZIP+4. Get those four lines right and the U.S. Postal Service’s scanners will read the piece and route it without human handling. Get them wrong and the mail slows down, comes back, or gets hit with a nonmachinable surcharge.
The Four Lines of a Business Address
Every domestic business address is built from the same components stacked in the same order:
- Line 1: Recipient’s name (or an attention line)
- Line 2: Company name
- Line 3: Street address and any secondary unit designator
- Line 4: City, two-letter state abbreviation, and ZIP Code
The recipient’s name and the company name sit on separate lines so the mailroom at the receiving end knows both where the piece is going and who inside the building should open it. Skipping either one is the most common cause of internal misdelivery.
On the street address line, put the building number and full street name, then the secondary unit designator on the same line if it fits. USPS Publication 28 lists the approved abbreviations: STE for suite, FL for floor, APT for apartment, RM for room, DEPT for department, and about twenty others.1United States Postal Service. Publication 28 – Postal Addressing Standards – C2 Secondary Unit Designators Only move the unit designator to its own line above the street address when the delivery line runs out of room.
The last line carries the city, the two-letter state abbreviation, and the ZIP Code. Use the full nine-digit ZIP+4 whenever you can; it narrows delivery to a specific group of addresses and, for bulk mailers, qualifies for per-piece postage discounts.2U.S. GAO. Postal Service’s Processing of ZIP + 4 Letters Receiving Postage Discounts The USPS ZIP Code Lookup tool will verify any address and return its ZIP+4.3USPS. ZIP Code Lookup
Formatting Rules That Keep Mail Machine-Readable
Left-align every line in a block. No indentation, no centering. Use a simple, readable font at 10-point or larger.4United States Postal Service. Business Mail 101 – Delivery Address
Uppercase is preferred on all lines because optical scanners read it more reliably; lowercase is technically acceptable but risks errors on automated equipment.5United States Postal Service. Publication 28 – Postal Addressing Standards – Section 212 Format For anything being printed in volume, use all caps.
Omit punctuation from the address block. No periods after abbreviations, no comma between city and state. The one mark you keep is the hyphen in the ZIP+4.6United States Postal Service. Publication 28 – Postal Addressing Standards – Section 222 Punctuation A stray dot or comma can be misread by the scanner as part of a character.
Mail that can’t be processed by machine gets hand-canceled and charged a nonmachinable surcharge. As of January 2026 that surcharge is $0.49 per piece on top of regular postage, and the fix is usually a formatting correction.
Where the Address Block Goes on the Envelope
The scanner reads a specific rectangle on the face of the envelope. Anything outside that zone is invisible to it. For a standard letter-size envelope, the address block must sit:7United States Postal Service. 202 Elements on the Face of a Mailpiece
- At least 1/2 inch from the left edge
- At least 1/2 inch from the right edge
- At least 5/8 inch from the bottom edge
- No higher than 2-3/4 inches from the bottom
Keep logos, taglines, and decorative printing out of the read zone. The scanner cannot tell a marketing line from a delivery instruction, and extra text inside that rectangle is one of the most common reasons a piece gets kicked out of automated sorting.
Attention Lines and “c/o”
When the mail needs to reach a specific person or department inside a company, an attention line handles the routing. It goes on line 1, above the company name.8United States Postal Service. Publication 28 – Postal Addressing Standards – Section: Attention Line Use ATTN followed by the name:
- ATTN JANE SMITH
- ACME CORPORATION
- 123 MAIN ST STE 400
- ANYTOWN NY 12345-6789
For a department instead of a person, write ATTN ACCOUNTS PAYABLE on line 1. Never drop the attention line below the city-state line or push it into a corner; both placements confuse the equipment and the mailroom.4United States Postal Service. Business Mail 101 – Delivery Address
The “c/o” (care of) designation is different. It tells the carrier to deliver the piece to one party on behalf of another, usually when the intended recipient doesn’t have their own address at that location. It sits in the same position as an attention line, above the name of the party at the physical address.
PO Boxes and Private Mailboxes at a CMRA
If the business receives mail at a Post Office Box, the PO BOX number replaces the street address on line 3. The Postal Service reserves the “PO Box” label for its own boxes.
Private mailboxes at a Commercial Mail Receiving Agency, like a UPS Store, are not PO Boxes and cannot be labeled as such. Use the CMRA’s street address on the delivery line and add either PMB or a # sign followed by the box number.9United States Postal Service. Publication 28 – Postal Addressing Standards – Section 285 Private Mailbox Addresses When the CMRA’s own address already contains a suite or other secondary element, use PMB rather than # in a three-line format:
- RECIPIENT NAME
- 456 OAK AVE STE 200 PMB 89
- ANYTOWN NY 12345
Getting this wrong routinely results in returned mail. If a CMRA is the official business address, check every place it’s printed, from letterhead to online listings, and confirm the format is consistent.
Return Address
Put the return address in the upper left corner of the envelope’s address side. It carries the same elements as the delivery address: name, company, street, city, state, and ZIP. The USPS recommends at least 8-point type.10United States Postal Service. Business Mail 101 – Return Address
A return address is not required on every piece of regular first-class mail, but it is mandatory on Priority Mail, Package Services, any mail with extra services such as Certified or Registered, and anything using a company permit imprint.10United States Postal Service. Business Mail 101 – Return Address Even when it’s optional, mail without a return address that becomes undeliverable simply disappears. For contracts, checks, and legal documents, always include one.
Military and Diplomatic Mail
Mail to overseas military installations and U.S. diplomatic offices uses APO (Army Post Office), FPO (Fleet Post Office), or DPO (Diplomatic Post Office). Domestic postage rates apply, but the format is specific:11USPS. Military and Diplomatic Mail
- Line 1: Recipient’s name and rank, for example CAPT JOHN DOE
- Line 2: Unit and box number, for example UNIT 2050 BOX 4190
- Line 3: APO, FPO, or DPO followed by AA, AE, or AP and the military ZIP Code
Do not include the name of the foreign country or city. Adding a country name can divert the piece into international mail processing, where it doesn’t belong.
International Business Mail
International addresses follow the same general logic, with the destination country name added as the very last line, in English, in uppercase.12United States Postal Service. Publication 28 – Postal Addressing Standards – Section A31 General Requirements That country line is what routes the piece out of the U.S. system and into the right foreign mail stream.
The USPS recommends a four-line format:13USPS. Description of the Format and Sequence of Information for the Recipient’s Address
- Line 1: Recipient name
- Line 2: Street address or post office box
- Line 3: City, province or state, and postal code
- Line 4: Country name in uppercase English
Many countries put the postal code before the city rather than after. Check the destination country’s own conventions before printing. For Canadian mail, put two spaces between the province abbreviation and the alphanumeric postal code.14Canada Post. ABCs of Mailing – Addressing
An international envelope containing only documents and weighing under 15.994 ounces as First-Class Mail International does not need a customs declaration form.15USPS. Customs Forms Anything heavier, or anything with merchandise or samples inside, requires one. Skipping a required customs form can cause the piece to be seized or returned with no postage refund.