I'm trying to develop an exhaustive list of possibilities - why Trump won't release his tax returns.
His income is less than he claims.
His tax liability and bracket are much lower than expected.
His income and assets are sheltered or hidden in offshore accounts.
He is in partnership with unsavory characters.
He has made illegal contributions from his political accounts.
His investments are tanking.
His bankruptcies are more numerous than expected and involve more money than known.
His charity donations are small.