Which line(s) on last year's (2021) 1040 do I use to calculate this years "safe harbor" estimated tax payments?

[Aquarius5]

For safe harbor, I understand that I need to make 4 equal estimated tax payments plus my W2 withholdings that in total are at least 110% of "last year's tax". I am unclear which line on last year's 1040 indicates that amount.

So I am clear how to cover safe harbor. 110% of last year's tax owed divided into 4 equal payments, or do I include tax withholdings from my paycheck and if so which pieces of those tax withholdings are included in the safe harbor calculation?

[Texas Roger]

Line 16 on form 1040 is the tax. Multiply your 2021 tax by 1.10 to determine what 110% of your 2021 tax would be. Subtract your estimated withholding from the 110% tax number to determine how much estimated tax to pay to have your total estimated taxes equal 110% of your prior year's taxes. 

CORRECTION: Line 24 is the correct line for tax paid in the previous year.  Unless your income is more than $150,000, you only need to pay estimated taxes totaling 100% of line 24. 

[Aquarius5]

Really line 16? I have seen other people indicating it's Line 24 "Total Tax" which includes child tax credit, self-employment tax, etc.

[ThomasM125 · Accepted solution]

Your total tax is listed on line 24 of your 2021 form 1040, that is the number you need to use to make sure you pay in enough estimated tax in 2022. You use the total of your tax withheld plus any estimated taxes paid to insure that you have paid in enough quarterly.

The applicable percentage you mention is 110% if your income is more than $150,000, otherwise it is 100%.

[fanfare]

please refer to instructions for Form 2210.

It will tell you exactly how to arrive at the amount for Line 8 prior year's tax.

OR 

rely on your tax software to compute the correct amount when you import your prior year's tax return.

[fanfare]

The 2021 Form 2210 instructions are not out yet.

On the other hand you haven't filed yet (unless you are really jumpy) and therefore you haven't finalized your 2021 total tax.

In other words, your first  2022 Estimated Tax payment is due in April.