Trying to figure out how much I gain or lose from the tax bill is difficult although any gain or loss will likely be rather small.
The first thing I look at is the overall difference between the current law's standard deduction+personal exemption (SD+PE) versus the new higher law's standard deduction. Under current law, the SD+PE for single filers is $6,350+$4,050, or $10,400 for 2017, and would rise $100 or $150 in 2018 compared to the new law's SD of $12,000 for 2018. Not a huge difference, maybe $1,500.
The breakeven point is if my itemized deduction (ID) is slightly higher than the current SD by about $1,500, or about $7,900. It just so happens that my ID has for several years been in the range of this amount. Going forward, if my would-be ID exceeds the old SD, then I will come out behind. The main driver of the variability in my ID is medical expenses. They spiked bigtime 2 years ago when I was in the hospital. But rising HI premiums and some smaller, unforeseen medical bills, also contribute to smaller spikes.
But my ID includes the full amount of my local property taxes, something for which I receive a state tax rebate the following year. That rebate has to be included as ordinary income, unfortunately, instead of a negative expense, because as income it is part of the AGI (and MAGI, for ACA subsidy purposes). If my ID is not sufficiently higher than the SD, it doesn't pay to itemize because I see my ACA subsidy reduced. This is where bunching helped out, giving me a little added tax benefit by juicing up my ID every other year while taking the SD in the others. If I end up taking the SD every year, I won't have to worry about this. It would also keep me further away from the ACA subsidy cliff, although large, unexpected cap gain distributions such as what's coming my way before the end of this year would push me over it anyway.
So......if I get sicker during the year and run up some extra medical expenses, then I may bunch some other deductible expenses and itemize, pretty much the same game plan I have now. I'd just have to get a lot sicker and run up more bills than compared to current law. Pleasant thought, huh?