Starting with tax frames the name as a professional service, the way an advisory firm lists its practice areas. Bitcoin, named directly, narrows the subject without the broader word crypto. The hyphen makes the boundary between the words explicit and helps when the name is read aloud: tax, hyphen, bitcoin. The .com ending, the global commercial default, suits a tool or firm whose clients file in more than one country.
The name belongs to the Bitcoin Tax & Law DACH collection and fits bitcoin-specific tax services. It suits reporting software focused on bitcoin wallets and second-layer payments, an advisory practice for miners and long-term holders, or an international knowledge base on how bitcoin income is documented. The same name is also held on the German ending, and both can be acquired together for an international and a German site.