Where do I check if I have some investment losses that I could not claim in 2017? I dont remember if I had any pending losses and not sure where to find that data.

You are allowed to deduct up to $3000 of capital losses against ordinary income, each year. Any excess is treated as a capital loss carry forward.

If you used TurboTax (TT) last year, that will happen automatically. A short term carry over will show on line 6 of Schedule D and a long term carry over on line 14. Your forms list will also have a carry over work sheet.

There's one other way to check this.  In TurboTax (TT), enter at:

- Federal Taxes tab 

 - Wages & Income

Scroll down to:

-Investment Income

   -Capital Loss carryover. Click start. The carry over box will be pre-populated with last years's amount. If you didn't use TT last year, you will enter your amount here.