I may be in a penalty situation for underpayment of 2020 taxes, on which line of my 2019 1040-SR do I find my tax liability?

[ms-ds]

Is tax liability the final amount owed to the IRS?  Or is it the total tax due prior to deductions for tax payments made i.e. FIT withheld from wages?

[VolvoGirl]

Total tax line 16.

[Mike9241]

per 2210 instructions add the following

from 2019 1040 or 1040-SR

Line 14,
Schedule 2 (Form 1040):

Line 4,

Line 6 (additional tax on distributions only),

Line 7a,* see below

Line 7b,

Line 8, don’t include the following write-ins:
• Uncollected social security and Medicare tax or RRTA tax on tips or group-term life insurance (identified as “UT”);
• Tax on excess golden parachute payments (identified as “EPP”);
• Excise tax on insider stock compensation from an expatriated corporation (identified as “ISC”);
• Look-back interest due under section 167(g) (identified as “8866”), and under section 460(b) (identified as “8697”);
• Recapture of federal mortgage subsidy (identified as “FMSR”); and
• Interest accrued on deferred tax under a section 1294 election for the year of termination (see Form 8621, Part VI, line 24, and the Instructions for Form 8621). Also subtract the amount from Form 8621, line 9c, that has been entered in brackets to the left of Form 1040 or 1040-SR, line 16.
* If you’re a household employer, include your household employment taxes on line 2. Don’t include household employment taxes if both of the following are true: (1) You didn’t have federal income tax withheld from your income, and (2) You wouldn’t be required to make estimated tax payments even if the household employment taxes weren't included.

for form 1040-NR total of the following

Line 53,Line 54,Line 55,Line 57 (additional tax on distributions only),Line 58,Line 59a,*Line 59b,Line 60, don’t include the following write-ins:
• Uncollected social security and Medicare tax or RRTA tax on tips or group-term life insurance (identified as “UT”);
• Tax on excess golden parachute payments (identified as “EPP”);
• Excise tax on insider stock compensation from an expatriated corporation (identified as “ISC”);
• Look-back interest due under section 167(g) (identified as “8866”), and under section 460(b) (identified as “8697”);
•  Recapture of federal mortgage subsidy (identified as “FMSR”); and
• Interest accrued on deferred tax under a section 1294 election for the year of termination (see Form 8621, Part VI, line 24, and the Instructions for Form 8621).

1040-NR-EZ line 15

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@ms-ds 

if you are in a penalty situation, TurboTax will put the non-zero penalty on line 38 of your 1040.

Phew!

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For purposes of estimated tax calculation, your prior year tax is from 2019 line 16.

TurboTax would carry it over if you used TurboTax last year.