I just realized today (12/31) that I was never billed for property taxes. Typically I get a paper bill in mid-December and I pay it immediately. I get two of them (one for my property and one for my share of a lake that's part of the HOA common property) and it's very unlikely that both went astray.
Figuring I'd never get a civil servant on the phone (it was 2 PM), I got on my bank Web site and set up a payment for a little more than what I paid last year. They payment info has Block and Lot Number detail from last year. Naturally they won't get it today- the bank mails a paper check. It won't be deducted from my account till the check is cashed.
Is it still a 2018 deduction? I'm hoping it is because if I include 2 years of property taxes plus state taxes in my 2019 return I'll be over the $10K SALT limitation and will lose about $4,000 in deductions.
A deduction is dependent upon whether it is due and owing and when it is paid, or if you are on the accrual basis of accounting for tax purposes when the liability meets the all events tests. So, if you owed the amount as of December 31 and made the payment on or before midnight December 31st then the real estate (property) tax would be a deduction. You tendered the payment in time and as long as the check is good the deduction is good. When the check gets cashed by the other party is not a consideration.