Thanks VolvoGIrl but that is not the problem. First of all, going into a “higher tax bracket” just affects the additional income, not the income which was in a lower bracket. A common misunderstanding. Whether this additional money was in the 22% or 24% bracket would not generate an increase of $12 in tax on $13 of income.
Second, I understand that a change in income can result in a loss of deduction or credits. That did not happen here. I added $13 of income, my taxable income went up by $13. My tax went up by $12.
Bottom line - TurboTax has a programming error. Their tax calculation without the $13 was a few dollars too low,. Their tax calculation with the $13 was a few dollars too high. Those two error compounded to result in the $13 having a 92% marginal tax rate.
The program can’t seem to do simple math.
