Estimated Tax Payments
If you are self-employed or have additional sources of income outside of your regular job, you may fall into the category of Americans who are required to file their Federal taxes not just once a year in April, but four times annually. Generally, you must pay estimated payments in four installments equal to 90% of your current year tax liability or 100% of what you paid in the previous year.
However, if the AGI on your prior year's return was more than $150,000 ($75,000 if married filing separately), the percentage requirement increases to 110% of last year's tax or 90% of current year tax, whichever is lower.
The minimum threshold for paying estimated tax is $1,000.
You may get a larger Federal deduction this year if you make your state 4th quarter estimated tax payment by December 31 (instead of by the required January 15, 2018). But, be wary of the AMT.