Why is the "2025 actual taxes" for 2026 estimated taxes different than my Total Tax amount?

[user17756657168]

When TurboTax calculates "100% (110%) of your actual 2025 taxes" as the method for estimating 2026 taxes, that amount is much smaller than my Total Tax on line 24 of 1040.  It appears that this is being calculated as [2025 Total Tax After Credits] - [2025 Withholding] - ["Other payments" (my Net Premium Tax Credit from schedule 3)] .  Is the really the correct amount for safe harbor?  I think I should use my Total Tax from 1040 line 24, especially since I will have no withholding this year, and also I will not have a net premium tax credit balance this year.  

[baldietax]

see instructions for Form 2210, Lines 1-3 etc, "tax" for safe harbor is generally based on 1040 Line 22 plus certain tax from Schedule 2, less refundable tax credits

https://www.irs.gov/pub/irs-pdf/i2210.pdf

Turbotax by default will use prior year tax for the ES vouchers and assumes 2026 withholding is the same as 2025; I am not sure how it handles tax credits but I would think it uses similar assumptions.  Under Other Tax Situations / Form W4 and Estimated Taxes you can provide estimates for 2026 income to optimize the ES voucher calculation based on 90% of 2026 tax instead of 100/110% of 2025 tax.  There have been some posts that this section is not applying updated withholding figures correctly so check the calculations.

You can also use other calculators like this as another source for 2026 estimates.

https://www.dinkytown.net/java/1040-tax-calculator.html

[user17756657168]

Thank you for the explanation. This approach does make sense in general. Since I know that the withholding and the net premium tax credit will not apply for me in 2026, I will just pay my estimated taxes directly to the IRS based on my 2025 total tax, without using TurboTax's calculation, because I don't want to owe money next year.