nondeductible adjective 1noun 1forms 1 adjective1 •That cannot be deducted for income tax purposes, and that tax has to be paid on.Since you fund a nondeductible IRA with already-taxed dollars, you might figure you wouldn't pay any income taxes on the conversion. — 2012 noun1 •Any expense that cannot be deducted for income tax purposes. formsnondeductibles
