What is a flat rate envelope?

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A Priority Mail Flat Rate Envelope is one of the United States Postal Service's flat rate packages which always ships for the same rate within the USA as long as your order fits inside the packaging. The flat rate envelope is intended for documents; if you want to ship something that isn't a document with USPS Flat Rate service, a Small Flat Rate Box may be more suitable.

Rates for Flat Rate Envelopes:

The cost to ship a flat rate envelope varies by rate tier (ie: Retail, Commercial Base, Commercial Plus), service (Priority Mail vs Priority Mail Express), destination (domestic vs international) and envelope type (ie: standard, padded, legal envelope). View our rate comparison table.

Where to find a flat rate envelope:

Flat rate envelopes can be found at your local post office, or ordered free online at


Related articles:

Flat Rate Envelopes - Rate Comparison (Rate Table)
What is USPS Priority Mail Flat Rate Forever Prepaid?
What is the most cost effective way to ship my packages via USPS?
USPS Supplies: Ordering Details (FREE)


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