Trump is not required to provide his tax returns.
If his returns are under audit, then releasing them could impair the IRS as well as Trump's right to challenge any IRS decision in court.
Any other party has to give permission for their information to be released that is in his files. According to the code section of Congress, it would have to be closed session.
Any disclosure by Congress and their staff carry severe penalties. The law may allow Congress to see them, but re-disclosure isn't granted unless there is a criminal element.
This section of law also hasn't been tested in court.
And the right of protection involving search and seizure is a Constitutional right. From court cases available, the IRS can secure info to enforce the tax laws. The courts dont accept the nut cases who think self incrimination protects them from paying tax.
However, the Congress request and intent may violate the search and seizure in the bill of rights.
Then, there is executive privilege and separation of powers. Also, Congress may lack power to enforce refusal to disclose. Only the executive enforces law, not the Congress.