First Class Letters & Flats

Teapplix USPS support printing First Class Letters & Flats. There are some special considerations when printing these type of labels.

1) Package Identification Number

First Class Letters & Flats do not have real tracking numbers. Instead they return a "Package Identification Number". This number can not be tracked on USPS site.

2) Physical Requirements

Typically, USPS requires merchandise to be shipped using First Class Package, and may reject your mail send in using First Class Letter, or First Class Flat. The "physical requirement" include that your mail piece have uniform thickness, and be able to "bend". The best source of this information is from the USPS site:, find the "Quick Service Guides", the current link is provided below but subject to change on USPS:

3) Confirmation to Customers

When you ship an order using USPS First Class Letter or Flat,  Teapplix will mark your order shipped on the marketplaces, but will not provide a tracking number. This is to avoid the confusion to the buyers.  Also some marketplaces such as Amazon have restricted requirement that all number set as tracking number must be trackable.

4) International

Teapplix does support printing international letters and flats. Notice for flats, USPS requires that the content type must be 'documents'.

5) Cancel a First Class Letter or Flat label

Currently if you are using Teapplix USPS,  the cancellation of a First Class Letter or Flat label has to be performed by Teapplix. Please contact Teapplix Support if you have such need.