As of June 1, 2018, The General Administration of Customs China (GACC) requires that all shipments include a Tax ID, also known as a Uniform Social Credit Code (USCC).
A USCC is an 18-character alphanumeric code that the consignor of a shipment is required to provide on all China Customs Advance Manifest (CCAM) filings.
Obtaining the USCC from your supplier along with your commercial invoice/packing list will help expedite the freight forwarder's processing of your shipment, otherwise, the forwarder will obtain the USCC directly from your supplier as part of their standard freight processing.