There is no legal requirement for a President (or candidate) to release their tax returns. Some have, by choice. Mitt Romney was forced to by Harry Reid accusing him of not paying taxes at all. Releasing Trump's tax returns not only includes himself, but his family, which is highly unfair to them. Also: what's in your tax returns is between YOU and the IRS. Not ANYONE else's business without a valid warrant (or court subpoena).