<prompt> Human: Heres the situation. My co-worker recently completed his taxes with Turbotax and noticed that his return was significantly less when he added his spouse. Before they add each other his return is at 2000 cdn and he is sitting in the lowest tax bracket with an income of 40,000. His wifes return is 3000 cdn and she is also in the lowest tax bracket with an income of 29,000.When they combine their return on Turbotax it drops their combined return to 360 dollars cdn. A massive drop! Can anyone explain the rational behind that difference? Are they being bumped into another tax bracket? Are they missing something fundamental? I dont have much experience with this and I know you folks have great advice. Any help you can provide would be educational!  <response>: I am not too familiar with TurboTax but what could have happened is that when your co-worker was filling out his return he put his marital status as married but didnt fill in his spouses net income. TurboTax would have automatically I believe the software does this, but again im not completely familiar with TurboTax assumed his spouse had 0 net income which would have made him eligible to claim the Spouse or Common-Law Partner Amount line 303. This allows you to claim a non-refundable tax credit if your spousecommon-law partner made less than 11,138. If he hadnt put her income in yet, then his refund would have been 1670 larger as this is 15 of 11,138. Since her income was actually 29,000 he would not have been eligible for this credit. This is one possibility but it still doesnt look right if both of their refunds dropped by that much. Any more information you can give us? What credits are they claiming? Do they have any dependants? Edit: Just realized Ontario is in the title woopsEdit2: Another possible reason for his spouses return is that if she did the same thing where she put married but didnt specify his income on the program then her refund would have looked larger because she could have been eligible for the Working Income Tax Benefit WITB. To be eligible for WITB she would have just needed to have her net income below 27,736 Ontario, family with no children threshold which could have been possible if she had any deductions like RRSP contributions. The amount wouldnt have been that large because I am sure her net income wouldnt be that far below the 29,000 that she actually took home although it is possible but it still would have changed the refund amount. And then she would be ineligible for the credit when the spouses income was input because they would be over the threshold. So two possible things that combined could have contributed to that large decrease. 