How do I start my 2018 quarterly tax return?

[DoninGA]

There is no quarterly tax return.

You can pay estimated taxes by quarter using IRS Form 1040-ES mailed to the IRS with your estimated tax payment.

Or you can use the IRS website for tax payments - https://www.irs.gov/payments

Go to this IRS website for a Form 1040-ES and use the worksheets for estimating the quarterly payments - https://www.irs.gov/pub/irs-pdf/f1040es.pdf

Or see this TurboTax support FAQ for estimated tax payments - https://ttlc.intuit.com/questions/2584228-can-turbotax-calculate-next-year-s-federal-estimated-taxes

Note - You will need the TurboTax online edition of Deluxe or higher for calculating estimated tax payments.

[VolvoGirl]

To prepare estimates for next year you start with your current return, but be careful not to change anything.  If you can't get back into your return, Click on Add a State to let you back into your retun.

You can just type W4 in the search box at the top of your return , click on Find. Then Click on Jump To and it will take you to the estimated tax payments section. Say no to changing your W-4 and the next screen will start the estimated taxes section.

Or Go to….
Federal Taxes or Personal (Desktop H&B)
Other Tax Situations
Other Tax Forms
Form W-4 and Estimated Taxes - Click the Start or Update button

To just estimate the remaining quarters put in that you paid $1 for the missed quarters so it will only calculate the remaining quarters.