Look up the address on the USPS ZIP Code Lookup tool
Check the full mailing address on a recent USPS mail piece
Use the ZIP+4 code shown by your address verification service
Search the address in an online postal address lookup
Contact the local post office for the ZIP+4 code
Ask the recipient or property owner for the full ZIP+4 code
Verify the address in your shipping or billing software
Use the USPS Address Information System if you have access