A CAIN is a Customs Assigned Importer Number used for foreign importers.

What is a CAIN?

A CAIN is a Customs Assigned Importer Number. If an importer is importing into the U.S. as a foreign importer of record and they do not have an EIN, Flexport can apply for a CAIN on their behalf. 

Foreign importers of record importing into the U.S. without an EIN will need a CAIN.