Postal Letter

USPS Priority Mail International Flat Rate Envelope Require Form 2976-E (plastic)?

I know that for Priority Mail international parcel require form 2976-E to put the 3 pages custom declaration. But for Priority Main international flat rate envelope, there's only 1 page. Can I use the 2976-E form instead just taping it on the outside? or I have to tape it on the outside? Thanks.

Public Comments

1. your post office would know.