I paid my property taxes for 2016 in Jan 2017. Am I allowed to deduct that on my 2017 returns ?
Also if I paid the 2017 taxes before December 31, 2017, then can I include both payments ?
You should deduct the property taxes in the year in which you actually paid them.
If you had two payments in a given tax year, then add them together and report the total in that tax year.
[Edited 3/10/2020 4:15 pm CDT - made year neutral]