US Address Format: The USPS Standard, Line by Line

The US Postal Service does not publish a rule saying “write the address like this”. It publishes a long technical manual, Publication 28, on how addresses should look after software has cleaned them. That difference matters. Most of the rules people quote as “the US address format” are really the output format of address-standardization tools, and you are free to be a little less strict on a handwritten envelope.

If you print labels, send bulk mail or store addresses in a database, though, the Publication 28 format is the one to copy. It is what USPS sorting equipment reads best and what every certified address tool will return.

The three lines of a US address

USPS calls them the recipient line, the delivery address line and the last line. The Universal Postal Union’s sheet on the United States gives this business example:

ABC MOVERS
1500 E MAIN AVE STE 201
SPRINGFIELD VA 22162-1010

Everything about the format is visible in those three lines. The directional (E) comes before the street name. The suffix (AVE) is abbreviated. The suite sits at the end of the street line, not on a line of its own. The last line runs city, state, ZIP+4.

The White House shows the post-directional case: 1600 PENNSYLVANIA AVE NW, WASHINGTON DC 20500. Leave out the NW and you have a different street. Washington has four quadrants, and the same street name and number can exist in more than one of them.

The last line: state code and ZIP Code

Publication 28, section 224, asks for at least one space between the elements of the last line and prefers two spaces between the state and the ZIP. One space is the minimum, so a label printed that way still meets the standard. The state is always the two-letter code: NY, CA, TX, DC, PR.

The ZIP Code has five digits. The optional ZIP+4 adds a hyphen and four more digits, 20500-0003, and that hyphen is the only punctuation the USPS punctuation rule keeps. Commas between city and state, full stops after abbreviations, the # in front of an apartment: all of it may be omitted.

One trap for software: ZIP Codes in New England, New Jersey and Puerto Rico start with zero. Boston’s 02134 becomes 2134 the moment a spreadsheet treats the column as a number. Store ZIP Codes as text. Always.

Abbreviations USPS actually uses

You do not need to memorise Appendix C of Publication 28, but the common suffixes and unit designators come up constantly. These are the standard forms:

A few designators need no number after them, according to the same appendix: BSMT (basement), FRNT, LBBY, LOWR, OFC, PH (penthouse), REAR, SIDE and UPPR. PH on its own is complete; APT without a number is not.

Where apartment and suite numbers go

The USPS section on secondary unit designators is short and worth following exactly. The preferred location is the end of the delivery address line. If that line would run too long, put the unit on the line immediately above the street, never below it:

MS JANE DOE
STE 1200
4500 NORTH FAIRFAX COUNTY INDUSTRIAL PARKWAY
SPRINGFIELD VA 22162

The street is invented to show a line that is too long for the unit to fit.

The pound sign is allowed but only as a stopgap. USPS says it should not be used if the correct designator (APT, STE, UNIT) is known, and when you do use it, a space goes between # and the number: # 4B, not #4B. Labels in the wild often skip that space, and standardization software rewrites them anyway.

If you collect addresses through a web form, the unit usually arrives in a separate “address line 2” field. That is fine for collecting, and you should join it onto the street line before printing. What belongs in address line 2 goes through the edge cases.

PO boxes, rural routes and military mail

Not every US address has a street. The UPU sheet lists the special forms USPS recognises:

• PO Box: PO BOX 34 on the delivery line, followed by DULUTH MN 55803-0034.
• Rural route: RR 3 BOX 9.
• Highway contract route: HC 72 BOX 293A.
• General delivery: GENERAL DELIVERY plus the city, in the UPU example with a ZIP+4 ending in 9999.
• Military: UNIT 2050 BOX 4190, then APO AP 96522-1215. A military code (AE for Europe, AP for the Pacific, AA for the Americas) replaces the state, and no city or country appears.

Military addresses count as domestic mail, so your form must accept APO or FPO (DPO for diplomatic posts) in the city field and the military codes in the state field. Some checkout forms reject them, which locks out service members stationed abroad and their families.

Format check versus deliverability check

Our free address format checker handles the left column: it flags a ZIP that is not five or nine digits, a missing state code or a missing house number, and prints the block in USPS order. The right column needs software that matches against USPS reference data. Google’s Address Validation API, for example, returns a delivery point validation code where D means the building was found but the apartment is missing, and S means an apartment was given but could not be confirmed. Options are compared in our piece on the address validation API market.

If you mail the same list repeatedly, deliverability also means keeping up with people who move; USPS handles that through NCOALink and its change-of-address data. Building validation and move updates into your own systems is a typical data engineering job, the kind of thing studios like OnlineBuilders take on.

Start smaller, though: take the last ten addresses your shop shipped to, run them through the checker, and see how many lack a unit designator or carry a ZIP Code that lost its leading zero.

Address format checker: Checks postcode format, house number and line order against the postal rules of the selected country, and prints the address in the format the post expects.