<prompt> Human: So, I sat down to do my taxes this year. I saw the same results with TurboTax and Taxslayer, so Im sure the math is right, but Im wondering what actually causes this.The basics are, two incomes, mine at 47,000 and my wifes at 26,000, for a total of 73,000. No kids, no additional dependents. We both claim a 0 for withholding which we verified, and hers actually has 25biweekly extra withholding. We dont do anything magic, so standard deductions have always been better than trying to itemize. This year was no different.I enter my W2, and it shows a nice refund of 1700. I add my wifes and it immediately drops to us paying in 135. Thinking I jacked up her numbers, I remove and redo it, producing the same result. So, I remove both W2s and add just hers back in. Again, nice refund of 1500. For some reason, though, both incomes on the form means we have to pay in.Can anyone shed some light on the situation?EDIT: Married filing Jointly. Trying married filing separately came out worse.Edit2: fixed the numbers.  <response>: Each job has its own separate W4, and assumes that its the only income you will receive. Theres no way for company A your job to know that you will receive extra income at company B your wifes job so they withhold based on your salary alone. Your wifes company B doesnt know you will be working and earning at company A so they withhold based on her salary alone, assuming that her tax bracket is low due to her lower income. Turns out that when you add her income to yours you made more than both jobs calculated for and thus your refund drops from a nice 1500 to 0.Most jobs offer a box on your W4 that says something like Additional withholding. This allows you to withhold extra to avoid situations like this. Hope that helps. 