As long as the withholding exceeded 110%

of the total tax due last year, you won't be subject to underpayment penalty.

However, the rules are more complicated than what you may think. The underpayment is calculated on a quarterly basis. If the company was sold in the first quarter, the IRS might make you pay penalty on the difference between 110% of your tax due last year and the withholding you had paid by the end of the first quarter.