Sorry to hear this. Maybe your new income affected your ability to claim certain deductions and since you lost those, your withholdings became irrelevant.

I don't mess around with the calculator.

Each year, I do an estimate of our taxes based on that year's expected income. Figure out my taxes for the year (dividends/interest earned, personal exemption, will we be standard vs. itemized deductions, etc.). I also adjust for health care, medical, 401k, and anything else tax free. Then I look at my what employer & my husband's employer is withholding per paycheck and multiply that by the pay periods. Then, as long as you are withholding at least 90% of your tax bill, then you don't pay penalties.

For example, here is what I do

Figure out estimated earned income, including bonuses (I also add in a modest amount for a pay increase that we typically get each year)

Subtract: 401k contributions, employer sponsored medical, flex spend contributions, dependent care contributions

Add back in: dividends, interest earned, any other income

This amount equals an approximate adjusted gross income

Subtract: standard ($12,400 for 2014) or itemized deductions if you have more deductions than $12,400; number of personal exemptions (2014 is $3950 per person)

Remaining amount is approximately your taxable income

From here, you can google the marginal tax rates for 2014 based on your filing status (married filed jointly, single, married filing separately). This is my favorite site for marginal tax rates since they already did the math and just find your taxable income:

http://www.forbes.com/sites/kellyphillipserb/2013/10/31/irs-announces-2014-tax-brackets-standard-deduction-amounts-and-more/This calculation should give you a rough idea of your federal tax bill for the year. Look at your paycheck and multiply your 2014 paycheck by the number of pay periods you have - that will tell you your estimated withholding. Add or decrease withholdings based on how far you are away from your estimated federal tax bill. I always make sure that I know the 90% rule to avoid penalties and add in some extra cushion in case things change throughout the year.

Hope this helps!