Forget the 14th Amendment. Here's a foolproof solution to keeping Trump from running again:

[StarfishSaver]

15. The 14th Amendment solution can be challenged and would get thrown out immediately

Congress cannot unilaterally find people guilty of crimes and bar them from office outside of the impeachment clause

And candidates are already required to file financial disclosures. Including tax returns as part of that disclosure is perfectly legal and constitutional.

The difference between the 14th Amendment option and the FEC option is that the former disqualifies a person from ever running by declaring them guilty of a crime, which can't be done with judicial involvement, while the latter doesn't affect anyone's qualifications to run but simply requires everyone who does run to do certain things, which is common and acceptable.

Candidates have to meet all kinds of requirements when they decide to run, including financial disclosures campaign finance disclosures, limitations on contributions, etc. This would be no different.