Property and state taxes for next year can not be prepaid but do I need to pay for state for this year early? Usually pay state estimate taxes by Jan 15th. But do I need to pay by end of the year instead? Also if I estimate too much state tax and get a refund, will I still be taxed on it next year?

Only thing I know to do so far is to pay mortgage earlier so interest can be written off and pay my zoo membership early.