I don't understand why I need to prepay my 2018 taxes.? I do have to pay Federal and State. Why did I get 2018 prepay coupons? My income will be much lower in 2018

[Carl]

Who says you have to pre-pay your 2018 taxes? There is no law I'm aware of that absolutely requires it, if you are not self-employed.

[AnnetteB · Accepted solution]

You can disregard the estimated payment vouchers that printed automatically with your return if you choose to. 

If you are at risk for an underpayment penalty next year based on your 2017 information, then the program will automatically calculate estimated tax payments and prepare the estimated payment vouchers for you.

You are not required to make those payments.  However, if you did have a balance due and your income is reported on a W-2, then you might consider changing your withholdings for 2018 to reduce your possible balance due for 2018. 

[edited 3/25/18 | 5:07 am PST to correct typo with date]

[ColoMtnMan]

"changing your withholdings for 2017 to reduce your tax liability." It won't change the tax liability. Just the amount of refund, if any. Decrease withholding to keep more of your income but reduce the refund, etc.