I do not pay estimated taxes quartley. Why am I being fined for my with holding being incorrect? Not enough withheld?

[fanfare]

Yes if your withholding is too low you will be subject to underwithholding penalty.

@EJAUBURN 

[John Dooley]

Anytime you pay less than 90% of the tax due, the IRS will assess a penalty. You need to adjust your withholding and make estimated payments if you have investment or other income sources

[Hal_Al]

Q. Why am I being fined for my with holding being incorrect?

A. The tax system is a "pay as you go" procedure. It doesn't matter if you pay by withholding or quarterly payments.  If you don't pay enough, there's an "underpayment penalty".