What Is a ZIP+4 Code? Nine-Digit ZIPs in Checkout Forms
A standard ZIP identifies a postal delivery area, while ZIP+4 adds a finer sector and segment. The extension may identify a building, part of a street, firm or group of boxes. It is address-specific: a city’s five-digit ZIP does not determine every recipient’s last four digits.
A standard ZIP identifies a postal delivery area, while ZIP+4 adds a finer sector and segment. The extension may identify a building, part of a street, firm or group of boxes. It is address-specific: a city’s five-digit ZIP does not determine every recipient’s last four digits.
✓ Key rules
- ZIP+4 has five digits, a hyphen and four more digits.
- The extension refines delivery routing; it is not a state code.
- Look up the full recipient address rather than guessing +4.
- Follow the form’s five-digit or ZIP+4 instructions.
Illustrative fields — replace with your recipient’s documented details
Destination Address
[Recipient]
[Street number] [Street]
[APT / STE, if applicable]
[City] [ST] [ZIP]-[4-digit extension]
UNITED STATES
Address fields and postal order
A standard ZIP identifies a postal delivery area, while ZIP+4 adds a finer sector and segment. The extension may identify a building, part of a street, firm or group of boxes. It is address-specific: a city’s five-digit ZIP does not determine every recipient’s last four digits.
- ZIP+4 has five digits, a hyphen and four more digits.
- The extension refines delivery routing; it is not a state code.
Form requirements and exceptions
Many ordinary checkout forms accept five digits; use the complete ZIP+4 when specifically requested or returned by USPS address lookup. Some postal products or mailing workflows have additional requirements. Keep leading zeros and use the hyphen when writing the full code. For billing, match the issuer’s records and contact the merchant if its validation rejects a valid address.
- Look up the full recipient address rather than guessing +4.
- Follow the form’s five-digit or ZIP+4 instructions.
Sources and official instructions
❓ Frequently Asked Questions
Which address and postal-code rules apply?
ZIP+4 has five digits, a hyphen and four more digits. The extension refines delivery routing; it is not a state code. Look up the full recipient address rather than guessing +4. Follow the form’s five-digit or ZIP+4 instructions.
What if the checkout rejects my address?
Select the correct destination first. Follow the merchant’s documented field requirements and contact support rather than inventing address components.
Check Country-Specific Address Rules
Select a country to view official postal line layouts, required fields, and postcode formats:
Explore Related Address Guides
What is Address Line 2?
Address Line 2 is an optional field on checkout and shipping forms used for apartment, suite, unit, or floor numbers. Learn what to put in Address Line 2 with visual examples.
What is Address Line 1?
Address Line 1 is the primary required address field on checkout forms used for your main street address, house number, and street name. Learn how to format it.
Address Line 1 vs. Address Line 2
Learn the exact differences between Address Line 1 and Address Line 2 with examples, comparison tables, and form placement rules.
What to Put for State/Province?
Stuck on a checkout form asking for State or Province? Learn what to enter for countries like the UK, UAE, Pakistan, Singapore, and Romania.
What to Put for State in Countries with No States?
Stuck on a required State field for a country with no states like the UK, Singapore, or UAE? Learn how to fill or bypass mandatory State/Province inputs.
City vs Suburb vs District in Address Forms
Confused by City, Suburb, or District fields on international shipping forms? Understand which field to fill based on your country's address format.
Billing Address vs Shipping Address
What is the difference between Billing Address and Shipping Address? Learn how card verification (AVS) works and when they can be different.
Can You Put PO Box in Address Line 2?
Can you enter a PO Box in Address Line 2? Discover when to put PO Box in Line 1 vs Line 2, and why FedEx/UPS reject PO Box deliveries.
How to Write Apartment & Suite Numbers
Learn how to write apartment, suite, unit, and floor numbers on shipping labels. See standard postal abbreviations (Apt, Ste, Unit, #) and placement rules.
What Does C/O Mean in an Address?
What does C/O mean in an address? Learn how to format 'Care Of' (c/o) for packages sent to guests, employees, or family members.
How to Fill Address Line 1 & 2 on Shein, AliExpress & Amazon
Having trouble filling Address Line 1 and Line 2 on Shein, AliExpress, or Amazon? Learn how to format international addresses for smooth delivery.
US Address Format for Apple ID & Digital Stores
Need to fill a US address for Apple ID, iTunes, Steam, or US billing? Learn the standard US address format, 2-letter state codes, and 5-digit ZIP codes.
ZIP Code for Dubai & UAE Addresses
Does Dubai or the UAE have a ZIP code? Learn how to fill mandatory postal code fields for UAE shipping addresses on Amazon, Shein, and DHL.
UK Address Format Guide
Master the UK address format: Learn where to put Building Name, House Number, Post Town, County, and UK Postcode on online shipping forms.
APO, FPO & DPO Military Addresses in Checkout Forms
APO, FPO & DPO Military Addresses in Checkout Forms. Use the exact unit, PSC or CMR and box supplied by the recipient.
W-9 & W-8BEN Address Fields: Residence vs Mailing Address
W-9 & W-8BEN Address Fields: Residence vs Mailing Address. W-8BEN line 3 must identify your actual tax residence, not a PO Box.
Fix Billing Address Mismatches: AVS, Stripe & PayPal
Fix Billing Address Mismatches: AVS, Stripe & PayPal. Check the billing street number and ZIP against the issuer’s current records.
International Shipping Addresses for DHL, FedEx & UPS
International Shipping Addresses for DHL, FedEx & UPS. Check each field’s actual limit; UPS WorldShip address fields allow 35 characters.
Canadian Addresses & Postal Codes in US Checkout Forms
Canadian Addresses & Postal Codes in US Checkout Forms. Use the recipient’s real postal code, not the A1A 1A1 pattern.
Japanese Addresses in English: Romaji & Seven-Digit Postcodes
Japanese Addresses in English: Romaji & Seven-Digit Postcodes. Use the recipient’s supplied romaji spelling rather than inventing a street name.
Ireland Address Format: Counties, Eircodes & Online Forms
Ireland Address Format: Counties, Eircodes & Online Forms. The first three characters are the routing key, not a county abbreviation.
German Addresses: House Numbers, c/o & DHL Packstation
German Addresses: House Numbers, c/o & DHL Packstation. Keep Straße and Hausnummer in that order, including any letter suffix.
Gate Codes, Buzzers & Delivery Notes: Address Line 2 Rules
Gate Codes, Buzzers & Delivery Notes: Address Line 2 Rules. Keep the unit number in the postal address even when you also give instructions.
Registered Agent vs Business Mailing Address on Forms
Registered Agent vs Business Mailing Address on Forms. Read whether the field requests a registered office, physical location or mailing address.
Saudi National Address & SPL Short Address Format
Saudi National Address & SPL Short Address Format. A Short Address has four letters and four digits. Use your registered SPL details, including district and city.
South Korea: English Road Name Address & 5-Digit Postal Code
South Korea: English Road Name Address & 5-Digit Postal Code. Use the current five-digit postcode, retaining leading zeros. Preserve building (-dong) and apartment (-ho) identifiers.
Australia: PO Box, Parcel Locker, State Abbreviations & Postcodes
Australia: PO Box, Parcel Locker, State Abbreviations & Postcodes. Write suburb, state abbreviation and four-digit postcode together. A PO Box and a Parcel Locker are different delivery services.
Mexico Address Forms: Colonia, Calle, Exterior/Interior & Código Postal
Mexico Address Forms: Colonia, Calle, Exterior/Interior & Código Postal. Calle is the street; número exterior is the building number. Preserve all five postal digits, including leading zeros.
Hong Kong Address Without a Postal Code: Checkout Form Fix
Hong Kong Address Without a Postal Code: Checkout Form Fix. Hong Kong does not operate a local postcode system. 00000 and 999077 are not Hong Kong postal codes.
Italy: Via/Piazza, CAP Postal Code, Comune & Province
Italy: Via/Piazza, CAP Postal Code, Comune & Province. Write Via or Piazza, street name, then house number. Use the correct province: examples include RM, MI, NA, TO and FI.
Spain: Calle, Número, Piso, Puerta & Código Postal
Spain: Calle, Número, Piso, Puerta & Código Postal. Calle is the street and número follows the street name. Put the postcode before the locality on an envelope.
Netherlands: Postcode 1234 AB, House Number & Addition
Netherlands: Postcode 1234 AB, House Number & Addition. A postcode has four digits and two uppercase letters. Copy huisnummertoevoeging exactly as registered.
Switzerland: Four-Digit PLZ / NPA / CAP Address Format
Switzerland: Four-Digit PLZ / NPA / CAP Address Format. PLZ, NPA and CAP are language labels for the postal code. Do not append internal database postcode additions to the label.