<prompt> Human: In a recent thread aboglehead wrote this as part of a discussion about misunderstandings related to withholding:If you have multiple jobs and inputting the second job decreases your refund, that likely means your second job didnt withhold enough.This isnt necessarily the case.This perplexing event can happen when you use tax software that shows interim refund values even if both your jobs are withholding more than enough. Its a misleading user interface issue in tax software thats worth pointing out.Its possible to have two jobs, not be underwithholding in either of them, and still see the interim refund value in tax software drop from a high value after youve input a first W-2 to a lower value when you add a second W-2.ExampleSuppose your total income from two jobs is 48,000 and you have a total withholding of 5400. Your refund is 175. Lets say this is what is happening in your two jobs:Job 1: income 24000, withholding 2700 Job 2: income 24000, withholding 2700Since you are getting a refund at the end of the year, and your jobs had exactly the same withholding for the same income, it makes sense to say both jobs were overwithholding, but just by a little bit. Id say this is a pretty good result for this taxpayer. He overpaid by only 175 during the year.Now lets observe why the interim results while entering data into a tax software can be deceiving and should be ignored. Lets enter the first jobs W-2:income: 24000 standard deduction: 6300 personal exemption: 4000 taxable income: 13700 income tax: 1598 tax withheld: 2700 refund: 1102Ive put the word refund into scare quotes because this interim value is a phantom. Indeed, Ive put the phrase income tax into scare quotes as well because its not accurate either.The problem with looking at this green 1102 interim refund value in tax software is that as soon as you add your second W-2 into the software, the value plummets down to 175. Its only that last value that is authentic.What happened to my refund? people cry.The peculiar thing is that if this taxpayer enters their second job W-2 into the software first, theyll see the same result. An apparent refund of 1102 plummets down to 175 when they enter their first job W-2. The issue is you must ignore interim results. Its not helpful to think that your tax is only 1598 for the first half of your income, because in our tax system someone who earns 48000 pays more than twice the tax that someone who earns 24000 pays. The reasons are several: we have tax brackets that charge more tax on higher amounts of income, and also we have standard deduction and personal exemption amounts that are only subtracted once from your income, not twice if you have two jobs.The withholding of 2700 in first job is actually correct for this taxpayer, even though it seems if you look at interim results that he only needs to pay in 1598 for this job. In fact, if this taxpayer had withheld 2500 from each job it would be underwithholding, even though 2500 is greater than 1598.This suggests why its important for taxpayers to use the Two EarnersMultiple Jobs worksheet on page 2 of Form W-4, or the IRS Withholding Calculator. If you set your withholding at one job to be correct just for that job, and you set your withholding at another job to be correct just for that job, theres a chance you will underwithhold overall. Even though if you enter each W-2 on its own into tax software it may seem to show you getting a refund, when you add both W-2s together the software will reveal you actually owe taxes.tldr: Taxpayers with more than one job or married filing jointly taxpayers where both spouses work should project their total tax liability and set their withholding appropriately for that, even though such amounts of withholding might seem excessive for the individual jobs if considered alone.  <response>: Ugh... I used to work at a tax office where the clients could see the refund changing on the screen, and would get mad when this happened. 