Updated 2026-10-22 · 5 min read
Address Line 1 vs Address Line 2
Address line 1 and line 2 are not two halves of the same street. Line 1 is the delivery point; line 2 is the secondary unit inside it. Getting the split wrong causes failed deliveries, rejected checkouts, and messy labels. Here is the rule and the edge cases.
The short rule
Line 1 = building number + street name (+ directional or street type). Line 2 = apartment, suite, floor, unit, room, building, or department. If there is no secondary unit, line 2 stays empty.
The rule matters because postal sorting equipment reads line 1 as the delivery point. An apartment number on line 1 can be mistaken for part of the street name, while a street name on line 2 can be ignored entirely.
| Address | Line 1 | Line 2 |
|---|---|---|
| 1234 SW Morrison St, Apt 5B | 1234 SW Morrison St | Apt 5B |
| 500 Market St, Suite 900 | 500 Market St | Suite 900 |
| 77 Broadway, Floor 3 | 77 Broadway | Floor 3 |
| PO Box 4421 | PO Box 4421 | (blank) |
Apartment, suite, floor, unit, room
Use the designator the building uses: Apt, Suite, Unit, Floor, Room, or Dept. Abbreviations are fine. Keep the designator and the number together so a label can print them on one line. “Apt 5B” is clearer than “5B” alone.
If the building has a tower or building letter, include it on line 2: “Tower B, Apt 1203”. If the form has a separate “Building” field, use that instead of cramming it into line 2.
Company names and attention lines
A company name is not a secondary unit. If a form has a separate company field, use it. If it does not, put the company name on line 2 above the street, or on the first line above the street address, depending on the label layout. Do not put a company name in the apartment field unless the form explicitly labels line 2 as “Company / Apt / Suite”.
An “Attention” line works the same way: it is not part of the street address. Put it above the street address or in the recipient name block.
PO boxes and military addresses
A PO box is a primary delivery point, so it belongs on line 1. Do not add a street address on line 2. If a merchant requires a street address, a PO box is not a substitute; use the address the merchant accepts.
APO, FPO, and DPO addresses use a specific format: name, unit or box number, APO/FPO/DPO, state abbreviation AE/AA/AP, and ZIP. The “state” is a military postal code, not a physical state. Follow the exact format provided by the military postal service.
How to test line 1 and line 2 in a form
Use one valid example, one address with a unit, one PO box, and one deliberately broken case. Check that the form preserves line 1 and line 2 separately and that the label output does not merge them. A synthetic fixture is enough for layout testing; do not use a real resident’s address.
- Valid street-only: 1234 SW Morrison St, Portland, OR 97205
- Valid with unit: 1234 SW Morrison St, Apt 5B, Portland, OR 97205
- PO box: PO Box 4421, Portland, OR 97205
- Broken: 1234 SW Morrison St Apt 5B, Portland, OR (missing ZIP)
Questions
- It will often still deliver, but it is the wrong field and increases the chance of a parsing or label error. Put the unit on line 2 when the form provides one.
- If the form marks line 2 as required but the address has no unit, enter a single hyphen or leave it blank if the form allows. Do not invent an apartment number. If the form rejects a blank line 2, that is a form bug worth reporting.
- Both are secondary unit designators. Use the one the building uses. “Suite” is common in offices; “Apt” is common in residential buildings.
- Use a dedicated company field if the form has one. Otherwise put it above the street address or in the recipient block, not in the apartment field.