<prompt> Human: Hi PF, I believe im in a bit of a pickle!Ive been in my career for about 2 years now and I just noticed 3 months ago I put a 1 instead of a 0 for my allowances on my W4 and had it corrected. Using the tax estimator at efile.com and punching in the info my pay stub has to date this year, it shows I will owe about 266 come tax time. since I dont know the numbers on my wifes W2 I am using the married filing separately setup. My only deductions I could use were my student loans interest.What im confused about is even though it was set to 1, shouldnt I not have a tax liability but be very close to 0? The only thing I can think of is my employer is not withholding enough. My FIT taxable amount on my last paycheck, with 0 allowances on my W4, was 1,070 and they withheld 71.17. That comes out to about 6.6. Shouldnt it be closer to 160 to meet the 15 tax rate im in?In case its not already obvious im pretty incompetent when it comes to taxes; if it werent for turbo tax I would be pretty lost. They really should be teaching this all in school.  <response>: Dont use married filing separately feature if you are really going to be filing jointly. It changes many things, and can definitely result in a larger tax liability. It wont give you a good estimate.Try the free TaxCaster app or web page. It has a simple interface. If you leave the withholding field empty, it can tell you your total tax. Then you can subtract your withholding to see whether you will be getting a refund. 