Isn't the deduction still allowed but capped at $10k? In which case, no way anyone in SG county not named Koch is going over that
In 2018, you will be able to deduct up to $10,000 in SALT or property tax (or maybe a combination of both - not sure). But the standard deduction will be doubled to $24,000 for married couples. So once you shrink the SALT deduction and double the standard deduction, there will no longer be any reason for me and a great many people to itemize. Which means that the property tax deduction is only valuable to us in 2017.
Based upon what I'm reading, the law
does allow you to deduct, in the 2017 tax year, prepaid 2018 property tax as long as it is paid in 2017. The only downsides are (1) stroking a big check that would otherwise be paid more gradually through your mortgage payments, and (2) if you move in 2018, you've paid the next owner's taxes for whatever portion of the year they own the home.
But those are small downsides to getting a deduction worth hundreds if not thousands of dollars. So if you fall in the above camp and 2017 is the last year the property tax deduction is valuable to you, you ought to look into prepaying 2018 taxes now.
And no, you can't do this for state income tax - that is prohibited by the law.