If you pay online today Friday Dec 29, Sat Dec 30, Sun Dec 31, 2017 or Jan 1, 2018 all payments will post in the tax office on Tuesday Jan 2, 2018. If you make an online payment in December 2017 be sure to keep the confirmation e-mail you receive and keep your bank statement or credit card statement to prove you made a December payment. The tax office does not receive online payments until the next business day which will be January 2, 2018.