The first safe harbor provision, meaning no penalties for underpayment, is (say we're talking about paying estimated taxes in 2023 for 2023 tax year):
Pay at least 100% of 2022's actual tax
The second one is:
Pay at least 90% of 2023's actual tax (requires good predictive capability).
If either one is met, no penalty. The above are for AGI's of $150,000 or less (same for singles, heads of households and married filing jointly).
For AGIs over $150,000 the first percentage is 110%. The 2nd one is the same 90%.
Edited to add If one's tax is less than $1000, or one's tax minus withholding is less than $1000 (don't count estimated payments, just withholding) one is safe. This from looking at the top of Form 2210 /END EDIT.
On paying a year's estimated taxes lumped late in the year: They calculate required tax payments on a quarter - by quarter basis (roughly, see p.3 of Form 2210). One can contest that, e.g. I have a lot of "income" in December because that's when I do Roth conversions and do my IRA RMD's (both count as taxable income), but then one has to fill out Form 2210.
https://www.irs.gov/pub/irs-pdf/f2210.pdf
A harsh experience from an earlier year with TurboTax: in that year I had a $3 underpayment penalty for federal. I could have contested that by filling out Form 2210, but then TurboTax would not let me file electronically and I'd have to print and mail it in. Obviously its not worth my time / expense for a $3 saving.
As for Minnesota, I had a $2 underpayment penalty. TurboTax would not let me file electronically, FFS, even though I wasn't contesting it. IOW, simply having a Minnesota underpayment penalty forced me to print and mail it in.
Edited to add: Both underpayment penalties resulted from paying too little early in the year, not because my payments in total were below the requirement. My total year cumulative payment did meet the requirement. /END EDIT
Dunno if TurboTax / Minnesota is still that stupid, that was 4 or 5 years ago. But probably.
Disclosure: I'm *NOT* a tax professional, just another anonymous message board rando.
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