Flat rate packages from USPS function like postage stamps. If your package is under a specified weight, it will get to its destination for one flat price. Flat Rate boxes have the same functionality through their "Forever Prepaid" boxes. As long as you own the box, you can ship it without any worries if the package will meet postage requirements.
USPS Forever Prepaid Flat-Rate Details
- Envelopes and packages are prepaid.
- Envelopes and packages sold in packs.
- The label includes your return address, so packages are not interchangeable.
- Buy online at USPS or at your local post office.
- Reusable even when postage rates increase.
USPS prices are subject to change and likely increase, at infrequent times.