For the first time in several years, I'm preparing the income tax filing for my family. Since a professional did the preparations last year, we had no electronic records to directly load into the software we bought for the preparations. Thus, I've entered some values by hand. During the software's "interview", it asked about our previous year's (2016) itemized deductions. I dug up the number from our 2016 1040 and entered it. Much to my surprise, our tax liability went up by a few hundred dollars. Zeroing out that entry reduces our tax liability.
The biggest itemizations (for both 2016 and 2017) were our mortgage interest, property tax, and state income taxes, with some charitable contributions also. There was no sort of carry over of deductions. The refund we received in 2017 for our 2016 state taxes is entered elsewhere as income.
With no sort of carry over, it makes no sense to me that our 2016 itemized deductions would have any effect on our 2017 taxes. Thus my question is why would this be? Or is there a bug in the software?