GBTC stands for Grayscale Bitcoin Trust. This is a publicly traded company that trades Bitcoin.
From their webpage:
Grayscale Investments®, the world’s largest digital currency asset manager and sponsor of Grayscale® Bitcoin Trust* (OTCQX: GBTC) (the “Trust”),
I believe you need to mark the response "yes". Don't mess with the crypto world. This is a high level audit focus of the IRS.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
