Yes, and they were accepted. A year or two ago I would have been less confident but now almost UX is happy to cite sources.

Not speaking to the wisdom of filing taxes using LLMs, but just FYI (assuming US here) taxes being accepted doesn't mean they were correct. It just means the IRS hasn't found anything major wrong (e.g. SSN used on multiple returns). Even being approved isn't a guarantee, an audit could come later.