MN S-Corp Owner here too. In fact, just moved back MN this month and so am contemplating Hennepin County prop taxes.
A few thoughts after way too much time anticipating this over the last month and doing intense calculations in the last couple days.
Prepaying income taxes - NoThe op asked about paying estimated taxes for 2017, not pre-paying but since this gets confusing to those that don't do estimated taxes and it was mentioned, I'm addressing it.
It's clear you can NOT pre-pay your 2018 state income taxes and get a deduction in 2017.
Paying (MAYBE) or Overpaying (PROBABLY NOT) 2017 taxes before Dec 31This is a complicated one.
Firstly, given the very high income of the OP, it's very reasonable to assume they are paying over $10k in state income taxes. If that's presumably the case in 2018, the moving any state income or property tax payments (more on that below) back to 2017 makes sense.
Remember that the payment date for state income taxes determines which year it's deductible within so paying Q4/2017 estimated income taxes in 2017 makes them deductible in 2017.
Another factor is tax rate arbitrage. If your tax rate is higher today than in the future, taking the deduction now is worthwhile. That's likely a factor as rates decline in 2018 but may also be driven by variable income of the company. In my case, we have a historically strong year in 2017. I hope, but wouldn't bank, on 2018 being better. So 2017, for us, is a higher income and higher rate year than 2018 is likely to be.
BUT... my income's no where near the OP's and I appear likely to trigger AMT. According to my calculations, any additional payment toward state income taxes will increase deductions for 2017 (great) but be negated by AMT (boo).
So, I'm going to pay my Q4/2017 estimated payments in 2018. That will ensure I've got at least $10k in state income taxes to deduct in 2018, even if our business has a down year.
Also, as a side note, overpaying state taxes shouldn't be excessive. Take care here if you choose to. Absent the AMT, it can recover the relative rate difference by the amount of the overpayment. IRS doesn't take kindly to massive overpayments though so this strategy, if not killed by your AMT and broader situation, may be useful but doesn't scale all that well.
Prepaying property taxesIn the meantime though, I'm going to prepay my property taxes to Hennepin County (today I think) and to our other home elsewhere. That plus not paying my Q4/2017 state taxes puts me right on the edge of AMT as best I can tell.
Meanwhile, even if it turns out not to have a tax savings, the fact that I pushed my Q4/2017 state taxes into 2018 thus surely hitting $10k on state income taxes alone means that any property tax deductions in 2018 would be lost no matter what so why not take the chance.
For those wondering about my speculation of my 2018 prop tax pre-payment being deductible or not, I'm referring to this
https://www.google.com/url?q=https%3A%2F%2Fwww.irs.gov%2Fnewsroom%2Firs-advisory-prepaid-real-property-taxes-may-be-deductible-in-2017-if-assessed-and-paid-in-2017&sa=D&sntz=1&usg=AFQjCNGqfVXnwWq7hNR0edoOb2Tbtwt6dg.
DAF - On another noteMy strategy instead is to take a bunch of long-term capital gain equities instead and dump them into our Donor Advised Fund. We staged this several weeks ago so we were ready to pull the trigger. Glad we did.
Since charity is not subject to AMT, that's a more effective tax strategy for our situation right now.
Sadly, we'll forgo charity for several years after this. It's a big move for us but one that we've been committed to for a long-time to make a bigger priority.
