Underpayment due to RSU sale

[WrkingMom]

I sold RSU last year and was assessed a penalty for tax underpayment. I sold more RSUs this year how to I caluculate the tax owed and how can I prepay to ensure no penalty this year.

[OmM1]

Hello WrkingMom

Tax laws require that we pay taxes, as we earn.

•  If you expect to owe more than $1,000 in federal taxes for the tax year, you may need to make estimated quarterly tax payments using Form 1040-ES, or else face a penalty for underpayment.
  
• If your federal income tax withholding (plus any timely estimated taxes you paid) amounts to at least 90 percent of the total tax that you will owe for this tax year, or at least 100 percent of the total tax on your previous year's return (110 percent for AGIs greater than $75,000 for single and separate filers and $150,000 for married filing joint), you most likely will not need to make estimated tax payments.
  
• If you don't calculate and pay your first estimated payment until after April 15, when the first quarterly payment is typically due, then you will need to make your payments as soon as you can to “catch up" but you might still have a penalty.

You can use your last year tax return and depending upon your situation (making more than 75K  for single or 150K for Married filing jointly) make sure that at the least you are paying 100% or 110% of last year taxes to avoid any penalty.

You may also your TAXCASTER - Tax Calculator 2022 to figure out your tax liability for this year.

It is advisable to have your payroll deduct any projected shortfall that you may have from your paycheck (this will avoid penalties for late payment of estimated taxes).

Please feel free to refer to the following article for a detailed discussion about estimated taxes

Estimated Taxes: How to Determine What to Pay and When 

Hope this helps you estimating and paying your estimated taxes to avoid any underpayment penalties.