US United States Major Cities Postal Codes

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📮 United States Postal Code FAQ & Postal Regulations

❓ Common FAQ

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What is the format of a US ZIP code?
Standard format is 5 digits (e.g., 10001). Extended format is ZIP+4 (9 digits like 10001-1234) with a hyphen.
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How to find the ZIP code for an address?
Use the USPS ZIP Code Lookup tool by entering the full address on the official USPS website.
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What happens if I use a wrong ZIP code?
Mail may be delayed, returned, or lost. For important documents, use USPS tracking and verify the ZIP code.
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Do ZIP codes ever change?
Yes, USPS may update ZIP codes due to regional adjustments. Always confirm your ZIP code after an address change.
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Is a ZIP code required for international mail to the US?
Absolutely. Always include the US ZIP code at the end of the address (e.g., New York, NY 10001 USA).

📋 United States Postal Regulations & Tips

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ZIP Code Writing Rules
Place the ZIP code on the last line with the state abbreviation (e.g., Los Angeles, CA 90001). Handwrite digits clearly without cursive.
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Package Size Limits
USPS rules: Longest side ≤108 cm, length + girth ≤165 cm. Oversized items require special mailing services.
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PO Box Requirements
PO Box addresses must include 'PO BOX + number' and correct ZIP code. Cannot receive large packages requiring signatures.
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Delivery Time Tips
Using ZIP+4 speeds sorting. Priority Mail delivers in 2-3 days, standard mail takes 5-7 days.
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Business Mailing Standards
Bulk business mail must meet USPS automation standards: address with correct ZIP+4, specific fonts, and paper specifications.