Your address is used for your SSN card, green card, bank cards, driver's license and tax forms. If it is wrong, important mail is lost.
How a US address is written
MARIA LOPEZ
1234 OAK ST APT 5B
SPRINGFIELD IL 62704-1234
Line 2: number, street name, street type (ST, AVE, BLVD, RD), and the unit: APT, UNIT or # with the number. Missing the apartment number is the most common reason mail goes back.
Line 3: city, the two-letter state code, and the ZIP code.
ZIP+4: the 5 digits plus 4 more (62704-1234). The extra 4 are helpful but not required. Find yours at usps.com with "Look Up a ZIP Code".
Online forms may have Address line 2 for the apartment number. Always fill it in.
In apartments, mailboxes are usually in a group (a cluster box). Get the key from the leasing office or landlord.
Packages that do not fit may go to a parcel locker in the same box (the key is left in your mailbox) or to the office.
In houses, the mailbox may be at the curb or on the house.
Put your name on the mailbox if allowed, and tell the landlord all names in the home.
Check mail at least every few days. Important letters (government, bank, court) come by post.
Informed Delivery from USPS is free. It emails you pictures of the letter-size mail coming to your address that day, and lets you track packages.
Open usps.com and search for Informed Delivery.
Create an account and verify your identity.
You can then see if a card or document is coming, and notice if it does not arrive.
A PO Box is a rented locked box at a post office. Useful if you move often or your mailbox is not safe. You pay by size and location for 3, 6 or 12 months, and must show two forms of ID. Some official forms need a physical home address, not a PO box.
Holding and forwarding mail
Hold Mail: the post office keeps your mail while you travel, from 3 to 30 days. Request it at usps.com.
Change of address (mail forwarding): when you move, mail is forwarded to your new address for 12 months. Online it costs $1.25 for identity verification; at the post office with PS Form 3575 it is free. It starts about 7 to 10 business days after approval.
Forwarding does not update your address with banks, schools or government agencies. Update each one yourself. Immigrants must also update their address with USCIS when they move (there are deadlines; check your status).
Forgetting the apartment number.
Paying a website that is not usps.com to change your address. Official online forwarding costs $1.25.
Leaving mail for days in a shared box; mail with personal information can be stolen.