USPS provides an integrated label ( label + customs form) that can be printed to Thermal Printer if all of the following criteria are met:
1. Has less than or equal to 5 items.
2. Shipping weight is less than or equal to 4 lbs.
3. Customs form declared value is less than or equal to USD 400
4. You ship using FCMI with Parcel/Flat/Letter OR you ship using PMI with Flat Rate Envelope/ Small Flat Rate Box