Deductions & credits

TT stands by its calculations.

 

9021– Reference Code for all math error conditions.

This is a bit of a misnomer, since the IRS considers it to be a  "math error" if you make a data entry mistake, or forget to claim some income; and thus the refund amount is incorrectly calculated..  The IRS will be sending you a letter explaining the change.  They do not notify TT.