I have a client with an inactive company, an S Corp, formed at the end of 2020. If it had been formed prior to 1/1/2020 it would qualify for the "inactive" exemption. The owner, a US citizen, lives in Europe. She does not use the company at all but does not want to shut it down just yet, as she may use it in the future. As of now she has NO US address.  She might return to the US one day or she could live abroad indefinitely. 

I do not know how to answer the question about what US street address to use for where the company does business. It does not do business anywhere, and if it were organized a few months earlier would not have to file.

Does anyone know what to do? 

I asked on the BOI website but all I got in response was a copy of the instructions.

>>The current U.S. Street address of its principal place of business or, for reporting companies whose principal place of business is outside the United States, the current U.S. address of the primary location from which the company conducts business in the United States (for example, a foreign reporting company’s U.S. headquarters). <<

NONE is the correct answer. It does not conduct business in the United States. It does not have US headquarters.