I'll be retiring this year and most of my income will be from stock/mutual funds. What product can I use to get an accurate picture of the estimated taxes I need to pay?

[FinallyInSeattle]

Currently have TurboTax Premier 2017

[TomYoung · Accepted solution]

That version will be fine.  You'll use the "W-4 and Estimated Taxes" interview under the "Other tax situations" tab.  (At least that's where it is on the desktop versions and I'm assuming "online" works similarly.) 

You'll enter your best estimates of what next year's income tax return will look like. Sounds like wage income and tax withholding will go down from 2017, maybe security sales with LTCG will go up.  TurboTax will show you your 2017 income tax actuals as a general guideline and you can adjust off of those numbers.  When you're done TurboTax will suggest various estimated tax scenarios designed to get you into one of the "safe harbors" to avoid being "underpaid."  (If you actually get into a safe harbor, generally keyed off last year's taxes or this year's taxes then you can owe the IRS a ton of money, but still won't be "underpaid" so you won't have to pay any underpayment penalties.)

If you have some months of withholding built into next year's estimates then the equal quarterly payments should be fairly low, for the first year of retirement.

Tom Young