Evidently your employer did not take out enough withholding to cover all the taxes on additional income from the vesting.
I doubt you have reasonable cause. you can try these options to see if your penalty is lower
1) annualized income page 3 of 2210
2) actual withholding for each period rather than the default of 25%
3) both 1 and 2
the simplest way to avoid penalties for 2024 is to have your withholding equal 100% of your 2023 tax. it's 110% if your 2023 adjusted gross income is over $150K
There are other ways such as withholding equal to 90% of your 2024 tax but you don't know this until you complete the 2024 return
This answer has been verified for accuracy by an Intuit expert employee
