Can you tell me how to put Nevada in Box 15-State on the 1099 form? This state is not listed.

A 1099-R form  (or any other form with NV in the state line)

You just leave every box on the state line entirely blank.

For a 1099-R, that means boxes 14, 15,16 all entirely empty.

(same goes for anyone else who lives in a state without an income tax)