Sorry! You can’t use USPS flat rate boxes unless you pay for the specific flat rate service marked on the box. If you don’t, USPS will charge you for the service marked on your box or envelope.
You Need to Pay for Flat Rate Postage If You Want to Use Flat Rate Boxes
USPS is very strict about paying for the exact shipping service that’s marked on your box or envelope. For example, if you have a Priority Mail Medium Flat Rate Box, that’s the service you need to pay for. You won’t be able to ship regularly Priority Mail, Priority Mail Express, or Parcel Select Ground in that box.
The same goes for Priority Mail Express flat rate envelopes! If you put something in a Priority Mail Express flat rate envelope and try to ship it First Class Package, guess what? USPS will charge you for Priority Mail flat rate postage.
For more information, check out our guide on paying for the service marked on your USPS branded boxes or envelopes.
Where Can I Get Flat Rate Boxes or Envelopes?
If you’re in the market for some USPS flat rate boxes or envelopes, you can pick them up for free at your local Post Office! You can also order them on USPS’ website, if you don’t feel like making the trek. Hey, we don’t blame you.