It would be helpful to know the taxable income and filing status, as an example of how the software is wrong.  And are you sure there are no capital gains reducing the amount to which the highest tax bracket applies?  

The tax calculation is accurate, and the Federal effective tax rate is correct. However, the tax planner incorrectly indicates the federal marginal tax bracket. It stated they were in the 22% bracket, while they were actually in the 24% bracket by $3,900 and $13,000. It also provides incorrect figures for income in the current federal bracket and the dollars needed to reach the next bracket.

For a single individual over 65 with a taxable income of $117,331, no capital gains, and a tax of $17,926, this places $13,980 into the 24% bracket.

The 22% bracket ends at $103,350 for 2025. The tax on that amount is $17,651. You’re coming up with $17,926 tax (just another $275) on another $13,980 income? I should have asked about qualified dividends, also.

They qualify for part of the senior exemption. The qualified dividends are offest with the capital loss.