Address Validation and Formatting
Address formatting rules, common validation errors, and how to fix them before sending mail.
USPS address validation is strict. Small formatting mistakes can prevent a letter from being accepted.
Recommended format
JOHN DOE
123 MAIN ST APT 4B
ANYTOWN NY 12345-6789Use these rules:
- Write apartment or suite information on the same line as the street address.
- Use standard abbreviations such as
ST,AVE,APT, andSTE. - Avoid punctuation except the hyphen in ZIP+4.
- Include unit numbers for multi-unit buildings.
Common validation errors
Address not deliverable
- Check for typos in the street name.
- Verify that the ZIP code matches the city and state.
- Confirm the address exists in USPS records.
Missing apartment or suite number
- Ask the recipient for the exact unit.
- Do not omit unit numbers for apartment, condo, or office buildings.
Invalid PO Box format
Certified Mail can be sent to PO Boxes, but format it as PO BOX 123.
Special cases
Military addresses
PSC 1234 BOX 12345
APO AE 09012-3456Business addresses
Put the company name on the first line and the recipient on the next line.
Rural routes
Formats such as RR 2 BOX 123 may be returned during standardization.
When to contact support
If the address looks valid but still fails, send support the exact input and the validation message you received.