Increasingly, foreign countries are passing legislation that requires certain customs numbers or codes to be included on packages, either identify the individual customer so tax can be collected, or identifying the marketplace that has already collected and remitted taxes. Some examples:
Brazil - CPF / CPNJ
South Korea - PCCC
Italy - CF / PEC
China - Resident ID
Australia - ABN
Norway - VOEC
Shipstation doesn't currently support any of this natively. There is no warning when shipping an order to these countries, there is no field to put this data, you're required to make your own workaround by just adding it manually to the company line of the address. Even worse, Shipstation address verification will often strip this information out entirely. The only advice given is to turn off address verification, which is not ideal.
Shipstation should be ahead of the curve and natively support these new changes to global shipping requirements. I'd expect a company whose focus is on shipping to be on the leading edge, keeping track of these new requirements and making sure that Shipstation users are compliant and not wasting time or money sending shipments that are not compliant and will create headache on the back end.