Knowing exactly where to place commas in an address is a fundamental writing skill that separates polished, professional correspondence from messy, ambiguous text. In real terms, whether you are addressing an envelope for snail mail, formatting a business letter, or writing a location within a sentence, the rules remain consistent: commas separate the distinct elements of a location to ensure clarity for both human readers and automated sorting machines. Mastering this punctuation prevents delivery delays and projects attention to detail.
The Core Rule: Separating Distinct Elements
The golden rule for address punctuation is simple: use a comma to separate the major components of an address. Specifically, you place a comma between the street address and the city, and between the city and the state (or province/region). You generally do not place a comma between the state and the ZIP code (or postal code).
Here is the standard structure for a United States address written on separate lines (envelope format):
Jane Doe
123 Main Street
Springfield, IL 62704
Notice the comma after "Springfield" (the city) but the absence of a comma between "IL" (the state abbreviation) and "62704" (the ZIP code). This is the standard endorsed by the United States Postal Service (USPS) and most style guides But it adds up..
Commas in Running Text (Inside a Sentence)
When an address appears inside a paragraph or sentence—rather than stacked on an envelope—the punctuation requirements increase slightly. You must treat the address as a series of appositives or parenthetical elements, requiring commas at both the beginning and the end of the insertion, as well as between the internal components Practical, not theoretical..
Correct:
Please send the package to 123 Main Street, Springfield, IL 62704, by Friday No workaround needed..
Incorrect:
Please send the package to 123 Main Street, Springfield, IL 62704 by Friday. (Missing the closing comma after the ZIP code).
Think of the full address as a single unit interrupting the flow of the sentence. Just as you would write "My brother, John, is here," you write "Send it to 123 Main Street, Springfield, IL 62704, please." The final comma signals the end of the address unit and the return to the main sentence structure Turns out it matters..
No fluff here — just what actually works.
Handling Apartment, Suite, and Unit Numbers
Secondary address designators—such as apartment numbers, suite numbers, or floor designations—follow specific comma conventions depending on the format.
On an Envelope (Stacked Lines)
The USPS prefers the secondary unit designator on the same line as the street address, separated by a comma if it doesn't fit on the first line, though modern Optical Character Recognition (OCR) technology handles it best without punctuation on the delivery line Worth knowing..
Preferred USPS Format (No comma on delivery line):
Jane Doe
123 Main Street Apt 4B
Springfield, IL 62704
Acceptable Alternative (If space requires a second line):
Jane Doe
123 Main Street
Apt 4B
Springfield, IL 62704
If you must place the unit number on the same line as the street address in a formal document or list, a comma is standard: 123 Main Street, Apt 4B Most people skip this — try not to..
In Running Text
When writing a full address with a unit number inside a sentence, treat the unit number as part of the street address component.
Her office is located at 123 Main Street, Suite 200, Springfield, IL 62704, on the second floor Which is the point..
International Addresses: Adapting the Logic
While the City, State/Province, Postal Code hierarchy is standard in the US, Canada, and Australia, many countries structure addresses differently. The comma rule adapts to the hierarchy: separate the specific from the general.
United Kingdom
UK addresses move from specific (name/house) to general (post town/postcode). Commas separate lines if written in a single string.
Format: Recipient, Building Name/Number, Street, Locality, Post Town, Postcode
Example: Mr. John Smith, 10 Downing Street, Westminster, London, SW1A 2AA
Note: No comma is placed between the Post Town (London) and the Postcode (SW1A 2AA) No workaround needed..
Canada
Canada Post follows a structure similar to the US but uses a space in the postal code.
Format: Recipient, Street Address, Municipality, Province, Postal Code
Example: Jane Doe, 123 Main Street, Toronto, ON M5V 2L7
General International Principle
If you are writing an address for a country you are unfamiliar with, apply the "Specific to General" rule. Place commas between every line element except the final two administrative/geographic units (usually the region/province and the postal code).
Special Cases and Exceptions
The "C/O" (Care Of) Line
When addressing mail "in care of" someone else, the "C/O" line acts as the recipient line. It sits above the street address. No comma is needed after "C/O [Name]" if it sits on its own line Not complicated — just consistent..
Jane Doe
C/O John Smith
123 Main Street
Springfield, IL 62704
In running text: Send it to Jane Doe, c/o John Smith, 123 Main Street, Springfield, IL 62704, immediately.
PO Boxes
A PO Box replaces the street address line. The comma rule remains: separate the PO Box from the City.
Jane Doe
PO Box 123
Springfield, IL 62704
Military Addresses (APO/FPO/DPO)
Military addresses treat the APO/DPO designation as the "City" and the two-letter code (AE, AP, AA) as the "State."
Private John Doe
Unit 1234, Box 56789
APO AE 09001
In running text: Write to Private John Doe, Unit 1234 Box 56789, APO AE 09001, for fastest delivery.
Addresses with "County" or "Parish"
In some regions (like Louisiana or the UK), a county or parish appears between the city and the state/postcode. Treat it as another layer requiring a comma.
Example (Louisiana): 123 Main Street, Baton Rouge, East Baton Rouge Parish, LA 70801
Example (UK): 10 High Street, Oxford, Oxfordshire, OX1 1AA
Style Guide Nuances: AP vs. Chicago vs. USPS
Different authorities have slightly different preferences, particularly regarding state abbreviations and the "ZIP code comma."
USPS (United States Postal Service)
The USPS is the authority for mail delivery. They strongly prefer no punctuation on the delivery address lines (street line and city/state/ZIP line) to maximize OCR readability That alone is useful..
- USPS Preference:
JANE DOE
123 MAIN ST APT 4B
SPRINGFIELD IL 62704
AP Style (Associated Press)
Used in journalism and news writing. AP uses traditional state abbreviations (e.g., Ill., not
