Yes, you can modify a flat rate box, it just won’t ship for the flat rate anymore. It will have to go priority by weight. If an FRE or FRB is presented at the office of mailing and the customer has manipulated or reconstructed it, the container is accepted using weight and zone — not the Flat Rate price.
Consequently, can you alter USPS Priority boxes?
Priority Mail boxes can be reused as many times as you like, as long as they are used for Priority Mail shipments. The USPS does not allow for its branded boxes to be used in the “wrong” service, so don’t use Flat Rate boxes for Priority Mail services, and vice-versa.
Likewise, is it cheaper to use a flat rate box or your own box? If within zone 3, 4, or 5 it is usually cheaper to ship regional rate boxes. If zone 7 or 8 then flat rate boxes are usually cheaper. If in zone 1 or 2 it is usually cheaper to use your own box up to 2 pounds and regional rate boxes over that. just use regular priority boxes.
In respect to this, can I cut down a flat rate box?
That which you quote is addressed specifically to flat rate. As long as you are paying priority rates they do not care if you cut them down or put 2 or more together. You may NOT use any free USPS product as interior packaging – i.e. small flat rate box inside a flat rate padded envelope.
What can be shipped in a flat rate box?
The Priority Mail flat rate boxes carry the most variety in size: from small windowed envelopes to large envelopes for legal documents, and small, medium and large boxes in side-loading and top-loading configurations.