Here's a December 27, 2017 advisory from the Internal Revenue Service concerning prepayment and deductability:
https://www.irs.gov/newsroom/irs-adv...d-paid-in-2017
Excuse me while I inject a wee bit of political humor here......hmmmm......hmmmm......my my my .... and hmmm .... is time for some serious reading comprehension here .....

.... "like who knew that redoing taxes could be so complicated .... duh?" ....... just who is that little, puffy, orange emoticon?
For a totally super-duper newspaper report on this IRS advisory, google this: New York Times, Dec 27, 2017: 'I.R.S. Warns That Prepaying Property Taxes Is a Risk' by Ben Casselman.