Offer your thoughts or opinion on the input financial query or topic using your financial background.

Stock grant, taxes, and the IRS
I went through this too. There's a safe-harbor provision. If you prepay as estimated tax payments, 110% of your previous year's tax liability, there's no penalty for underpayment of the big liquidity-event tax liability.  https://www.irs.gov/publications/p17/ch04.html That's with the feds. Your state may have different rules. You would be very wise indeed to hire an accountant to prepare your return this year. If I were you I'd ask your company's CFO or finance chief to suggest somebody.   Congratulations, by the way.