How to Write a U.S. Mailing Address: Apt, State, ZIP Code

Before submitting an order or form, confirm the street number, unit, city, state abbreviation, and ZIP Code as one complete address.

 Information checked October 15, 2026. Address formats can vary by property, carrier, retailer, government agency, and online form. Use the exact address assigned to your location and verify it before mailing or ordering.

A U.S. mailing address can feel backward when the address system you already know begins with a larger region and ends with a building. In the United States, the delivery line normally begins with the building number and street name. The city, two-letter state abbreviation, and ZIP Code appear later.

That order surprised us when we first entered U.S. addresses. Different websites also divided the same information into different fields, so Address Line 1 and Address Line 2 did not always seem consistent. Being asked for a state abbreviation was another confusing moment before abbreviations such as KS for Kansas and MO for Missouri became familiar.

This guide explains the basic format, apartment and unit numbers, state abbreviations, ZIP Codes, online forms, envelopes, packages, return labels, and centralized mailboxes. It uses format-only examples rather than real personal addresses.

Quick answer: A common residential format is the recipient’s name, then the building number and street name with any apartment or unit identifier, followed by the city, two-letter state abbreviation, and ZIP Code. Do not copy a generic example exactly—use the spelling and unit information assigned to the real delivery location.

The basic U.S. mailing address order

USPS Publication 28 describes three basic lines for a consumer or residential address: the recipient line, the delivery-address line, and the last line containing the city, state, and ZIP Code. A format-only example looks like this:

JORDAN LEE
123 MAIN ST APT 4B
CITY ST 12345

Do not mail to this example. Replace every element with the verified recipient information. The example only shows the order:

1. JORDAN LEE: recipient’s name;
2. 123: primary building or street number;
3. MAIN ST: street name and street type;
4. APT 4B: apartment identifier and number;
5. CITY: USPS-recognized city name;
6. ST: the appropriate two-letter state abbreviation; and
7. 12345: the five-digit ZIP Code.

The order can feel reversed compared with address conventions used in other countries. Instead of trying to translate an overseas address pattern word for word, treat each U.S. field as a separate data element and rebuild the address in the order requested.

The detailed standards are available in the USPS Publication 28 addressing guide.

What belongs in Address Line 1 and Address Line 2?

Online forms are not perfectly standardized. One site may provide a separate field labeled Apt, Suite, Unit. Another may provide only Address Line 2. A third may expect the apartment information on the same line as the street address.

Form field	What commonly goes there	What to check
Full name	The person or organization receiving the item	Use the name the recipient or account requires
Address Line 1	Building number and street name	Include directionals or street suffixes that are part of the assigned address
Address Line 2	Apartment, suite, unit, building, floor, or similar secondary information	Leave it blank when there is no secondary information
City	The recognized mailing city	Use the city shown by the address provider or USPS lookup
State	Two-letter postal abbreviation	Do not guess from a city name
ZIP Code	Five digits, or ZIP+4 when supplied	Confirm that it matches the complete street address

Follow the labels on the specific form. If it offers a dedicated apartment field, use it. If it has only one address line, include the unit after the street address, such as 123 MAIN ST APT 4B. Before submitting, review any formatted-address preview the website displays. Make sure the unit number was not dropped, duplicated, or moved into the wrong field.

USPS prefers a secondary unit designator at the end of the delivery-address line. If the entire delivery line does not fit, Publication 28 allows the secondary information on the line immediately above the street-address line. The important goal is a complete and unambiguous delivery address, not forcing every website to use the same screen layout.

Apartment, unit, suite, building, and the # symbol

Secondary information identifies one destination within a larger property. USPS lists standard designators that include:

• APT — apartment;
• UNIT — unit;
• STE — suite;
• BLDG — building;
• FL — floor;
• RM — room; and
• DEPT — department.

Use the designator provided by the property, business, recipient, or USPS lookup result. Do not automatically change UNIT to APT or invent a building number because another property uses one. USPS advises using the correct designation instead of a pound sign when that designation is known. If # is used, leave a space between it and the secondary number.

See the full USPS secondary unit designator guidance.

Why does the state use only two letters?

U.S. mailing addresses normally use the official two-letter postal abbreviation rather than a self-created abbreviation. Examples include:

• Kansas — KS
• Missouri — MO
• California — CA
• New York — NY
• Texas — TX
• Florida — FL
• Washington — WA
• Illinois — IL

These codes are not always the first letters someone would guess. For example, Nebraska is NE, Nevada is NV, and Alaska is AK. Check the USPS list of state and territory abbreviations instead of guessing.

What is a ZIP Code, and is ZIP+4 required?

A standard ZIP Code contains five digits. ZIP+4 adds a hyphen and four more digits that can identify a more specific delivery segment. A website may accept either format, but use the exact result provided for the address when one is available.

Do not assume every address in one city has the same ZIP Code. Large cities can have many, and a mailing city name may not match the municipality name a newcomer expects. The official USPS ZIP Code Lookup can search by street address or by city and state. USPS notes that a ZIP Code lookup confirms the code associated with an address; it does not prove that a particular person or company is located there.

A five-step method for entering an address online

1. Copy from a trusted source. Use the lease, utility account, housing office, recipient, government document, or an official USPS result rather than relying only on memory.
2. Separate the elements. Identify the building number, street name, unit, city, state abbreviation, and ZIP Code before filling the form.
3. Follow the form’s labels. Use a dedicated apartment field when provided; otherwise use the address-line instructions shown by that site.
4. Review the standardized suggestion carefully. Some websites suggest a corrected address. Compare every element before accepting it, especially the apartment or unit.
5. Save and recheck the final version. Confirm the address displayed on the order, account, or confirmation email—not only what you remember typing.

A bank may also ask for proof of your current address during account opening. Our guide to opening a U.S. bank account explains which identification and address documents to confirm before visiting a branch.

This final review is especially useful when opening utilities or internet service because a provider may distinguish the mailing address, service address, billing address, and shipping address. Our U.S. utility setup guide explains what to verify before choosing a start date or installation.

A card’s billing address is also important when paying. The guide to using a foreign credit card in the United States explains why a U.S. gas pump may request a billing ZIP code and why a shipping address should not replace the address held by the issuer.

Your mailing address does not always reveal the mailbox location

Knowing the written address does not necessarily tell you where to collect letter mail. Some houses have individual curbside boxes. Apartment buildings may have an indoor mailroom. Other residential communities use centralized cluster mailboxes and parcel lockers.

In our housing area, many mailboxes were grouped together along a road rather than placed directly at each home. We did not know that at first and spent time looking for our mailbox. The written address itself was not difficult; the missing piece was understanding the local delivery setup.

A correct street address does not always mean letter mail will arrive at the front door; confirm the mailbox location and key process after moving in.

After moving, ask the landlord, property manager, housing office, prior resident, or local Post Office:

• Where is the assigned mailbox?
• Who provides the key?
• Which box number is assigned to the residence?
• What happens when a package is too large for the individual compartment?
• Are private carriers directed to the door, office, package room, or another location?

USPS explains that centralized units can contain individual locked boxes and parcel lockers. Key responsibility can depend on who owns and maintains the mailbox. Read the USPS guidance on locked and cluster mailboxes for the general process, then verify the arrangement for the actual property.

Mailbox keys, utility deposits, administrative charges, and other setup details can appear around the same time. The apartment move-in cost checklist can help organize those questions before receiving the keys.

How to address an envelope or package

For a physical envelope or package, keep the delivery address legible and on the same side as the postage. USPS recommends placing the recipient address in the center area and the sender’s return address in the upper-left area. The return address tells USPS where an undeliverable item should be returned and is required for certain mail classes and services.

A simple layout is:

SENDER NAME
SENDER STREET AND UNIT
SENDER CITY ST ZIP

RECIPIENT NAME
RECIPIENT STREET AND UNIT
RECIPIENT CITY ST ZIP

Write or print clearly, keep all required labels on one flat side of a package, and do not fold a shipping label over an edge. USPS provides additional illustrations in its package preparation guide and mailpiece addressing guide.

What if a return label is already printed?

A retailer or marketplace may provide a prepaid shipping label containing the destination, return-routing information, barcode, and postage. Follow the return instructions for that specific order. Do not cover the barcode, fold the label over an edge, or add a second destination address that could create confusion.

In one of our Amazon returns, the instruction was to print the supplied document and attach it to the package. We followed the provided label rather than handwriting a separate return destination. That experience should not be confused with personally composing a return address from scratch: the merchant had already created the routing information.

If the label names a carrier you do not recognize, our USPS vs UPS vs FedEx guide explains who can use a mailbox, why Amazon deliveries arrive in different places, and how to choose the correct return location.

Return methods and deadlines differ by order and retailer. Our U.S. returns and refunds guide explains why one return may require a printed label and drop-off while another may use a different method.

Military housing address versus APO, FPO, or DPO

Living on or near a U.S. military installation does not automatically mean every mailing address uses the overseas military format. Domestic installation housing can have an ordinary assigned street address with a city, state, and ZIP Code. Use the address supplied by housing management, the sender, or the relevant account.

APO, FPO, and DPO addresses follow a specialized format. USPS says those addresses replace the city with APO, FPO, or DPO and use AA, AE, or AP in the state field. Do not convert a normal domestic housing address into an APO/FPO/DPO address unless the recipient or responsible office gives you that address.

Common address mistakes to avoid

• Leaving out an apartment, unit, building, or room number
• Putting the recipient’s phone number in an address field
• Guessing a state abbreviation
• Using the wrong ZIP Code for a street address
• Confusing a billing address with a shipping or service address
• Accepting an automatic correction without checking whether the unit survived
• Repeating the apartment number in two fields
• Using a building’s nickname instead of the assigned delivery address
• Assuming the mailbox is located at the front door
• Reusing an old saved address after moving

Final address checklist

Before ordering, mailing, or submitting a form, confirm:

• recipient name is correct;
• building or street number is present;
• street name and directional are complete;
• apartment, unit, suite, or building identifier is included when required;
• city name matches the assigned mailing address;
• state uses the correct two-letter abbreviation;
• ZIP Code matches the full address;
• the form did not duplicate or remove a line;
• the final confirmation displays the intended shipping, mailing, billing, or service address; and
• the mailbox or package-delivery location is known.

Frequently asked questions

Should the apartment number go on Address Line 1 or Line 2?

Use the form’s dedicated apartment, suite, or unit field when one exists. If the form has only one address line, include the unit after the street address. USPS prefers the secondary unit designator at the end of the delivery-address line, but online screens may collect the same information in separate fields before formatting the final label.

Can I write the full state name?

Some forms may accept it, but U.S. mailing addresses conventionally use the official two-letter postal abbreviation. When the form specifically asks for a state code, enter the two-letter abbreviation.

Is ZIP+4 required for every personal letter or online order?

Not every consumer form requires ZIP+4. A correct five-digit ZIP Code is commonly accepted, while ZIP+4 can identify a more specific delivery segment. Use the complete version when it is provided or required, and verify it through USPS when uncertain.

Does a correct address guarantee delivery to my door?

No. Letter mail may go to a curbside box, mailroom, cluster mailbox, or other assigned receptacle. Packages may follow different procedures depending on the property and carrier.

Should I type my address in all capital letters?

USPS addressing guidance favors clear, readable formatting and commonly presents standardized addresses in capital letters without punctuation. For an online account, follow the site’s instructions; accuracy and completeness matter more than manually changing capitalization when the system reformats it.

Final takeaway

Writing a U.S. address becomes easier once you stop viewing it as one long sentence. Break it into recipient, street number and name, secondary unit, city, two-letter state abbreviation, and ZIP Code. Then check how the specific website or mailpiece wants those elements arranged.

For newcomers, the unfamiliar parts may be the order, the state code, or the difference between an address and the physical mailbox location. Verify each element from a trusted source, inspect the final formatted address, and confirm where mail and packages are actually delivered after moving in.

This article provides general educational information. USPS standards, property procedures, online forms, carrier practices, and retailer return instructions can change or vary. Verify the current requirements for the specific address and shipment.