The safe harbor requires you pay 100% of the prior year taxes not 90% ... so review the calculations ... did they take into consideration withholdings from some other source like wages that did not happen as expected ?
The following is the general rule:
You must pay estimated tax for 2021 if both of the following apply.
- You expect to owe at least $1,000 in tax for 2021 after subtracting your withholding and tax credits.
- You expect your withholding and tax credits to be less than the smaller of:
- 90% of the tax to be shown on your 2021 tax return, or
- 100% of the tax shown on your 2020 tax return. Your 2020 tax return must cover all 12 months.
Note: If your AGI for 2020 was more than $150,000 ($75,000 if your filing status for 2021 is married filing a separate return), substitute 110% for 100% in (2b)
