Put the apartment number on the same line as the street address

Type your street address first, then add a comma, space, and the apartment number. The format is: 123 Main Street, Apt 4B or 123 Main Street, Unit 4B. Both "Apt" and "Unit" work — most systems accept either one.

This single-line format works for online forms, shipping labels, and address fields in most software. The postal service reads it correctly, and delivery drivers know to look for the apartment number after the street address.

Key Takeaways

  • Write the street address, then a comma and space, then "Apt" or "Unit" followed by the apartment number on the same line.
  • Do not put the apartment number on a separate line unless the form has two separate address fields labeled "Street" and "Apt/Unit".
  • Use abbreviations like "Apt," "Unit," "Suite," or "#" — all are recognized by postal systems and delivery services.
  • If a form has a second address line, use it for the apartment number only, leaving the first line for the street address alone.

When a form has two address lines

Many online forms split the address into two fields: one for the street address and one for "Apartment, Suite, or Unit." When you see this layout, put only the street address in the first field and the apartment information in the second field.

In this case, type 123 Main Street in the first field and Apt 4B (or just 4B) in the second field. The form is designed to separate them, so follow that structure. This is common on shipping sites, banking portals, and government websites.

Abbreviations that work for apartment numbers

You can use several abbreviations for apartment information, and postal services recognize all of them. The most common are Apt (apartment), Unit, Suite, and # (number symbol). Choose whichever fits the space available or matches what the form suggests.

Examples: 123 Main Street, Apt 4B | 123 Main Street, Unit 4B | 123 Main Street, Suite 4B | 123 Main Street, #4B. All of these reach the same address. If the form has limited space, the number symbol takes up the least room.

What not to do with apartment numbers

Do not put the apartment number on a separate line below the street address unless the form specifically has a second field for it. Handwritten envelopes can get away with this, but online forms and address fields need everything on one line or in the designated fields.

Avoid writing the apartment number before the street address — Apt 4B, 123 Main Street is incorrect and may cause delivery problems. Also do not use symbols like parentheses or slashes: 123 Main Street (Apt 4B) or 123 Main Street/Apt 4B can confuse automated sorting systems.

Typing an address with a building name

If your building has a name, you can include it before the street address. Type it like this: The Riverside Apartments, 123 Main Street, Apt 4B. The building name comes first, followed by the street address and apartment number on the same line.

Building names are optional — the postal service does not need them to deliver your mail. But including the name can help if your street address is shared by multiple buildings or if the building name is how your neighbors refer to the location. If space is tight, leave the building name out and stick with the street address and apartment number.

Fixing an address you already typed wrong

If you typed your apartment number on a separate line or in the wrong order, go back and edit it before you submit the form. Most websites let you change address information before checkout or before the form is sent. Look for an "Edit" button or click directly on the address field to make changes.

For shipping orders that have already been placed, contact the company's customer service right away — the sooner you report the error, the better the chance they can correct it before the package ships. For mail or packages already in transit, contact your local post office with the correct apartment number so they can deliver it to the right unit.

Frequently Asked Questions

Do I need to write "Apt" or can I just put the number?

You can do either. Writing "Apt 4B" is clearer, but just "4B" works too if space is limited. The postal service understands both formats. If the form has a separate field for apartment information, you can put just the number there.

What if my apartment is listed as a suite or unit instead of an apartment?

Use whatever term your lease or building uses. "Suite," "Unit," and "Apt" are all recognized by the postal service. Type it the same way: street address, comma, space, then Suite or Unit followed by the number.

Should I capitalize "Apt" or "Unit"?

Capitalization does not matter for delivery. "Apt," "apt," "APT," and "Apartment" all work. Most people capitalize it out of habit, but the postal service reads it correctly either way.

What if the form only has one address line and no apartment field?

Put everything on that one line: 123 Main Street, Apt 4B. This is the standard format and works in nearly all systems. If the form keeps rejecting it, try removing the comma: 123 Main Street Apt 4B.

Can I use a pound sign (#) instead of writing "Apt"?

Yes. 123 Main Street #4B is a recognized format. It takes up less space and the postal service understands it. Some people prefer it for online forms with character limits.