I suggest that you plan to send estimated taxes to the IRS following quarters when you receive large compensation (e.g. bonuses or large stock compensation).  The withholding rate on bonuses is now generally 22% (bonuses above $1 mil. have a higher rate).  Based on your income, that means that you are under withheld ~ 13% on your bonuses or stock compensation (you were in the 35% marginal rate).   I suggest that you pay estimated taxes of an additional 10-15% of your bonuses or stock compensation following the quarter ended where you receive large compensation to make up for the under withholding.  This will avoid the surprise tax hit when filing your income taxes and will help to avoid underpayment of estimated tax penalties.  I do not suggest adjusting withholdings as your allowances most likely are appropriate for your salary.   Quarterly estimated taxes are generally due April 15th, June 15th, September 15th & January 15th (following year end) but they can be paid sooner.  

I like to have my clients avoid penalties for many reasons.

 

1.  Avoid IRS correspondence

 

2.  Stay compliant with rules which allows 

 

3.  Avoid having to pay the penalties (sometimes of which are not that large)