Usually the broker sends 3 things --1099DIV, 1099INT and 1099B
Go to Forms mode in upper right and and then look at 1099B and the Form 8949 or 1099B in the left side where the Forms are located.
Many K-1's actually did not have to be sent to people until March 15th so you are probably correct in that it was not reported on the return filed.
You will need to Amend the return and after the Amended process is started go to:
Wages and Income
and scroll down to K-1 section to report.
For details on Amending a filed return see below:
Follow these directions:
- Open the return you want to amend in your TurboTax software program.
- Make sure your return is exactly as it was when you originally filed it.
- If you made changes after you filed, undo them. We suggest comparing your onscreen numbers with a paper copy of your filed return.
- Now, make an "amend" copy your return by selecting Save As (Mac: select Duplicate) from the File menu. This preserves the originally-filed return.
- Name the copy to distinguish it from the original, e.g., 2018 Amended Smith B Form 1040 Return or similar.
- You should now be working inside the copy you'll be amending. Inside your program, search for amend and then click the "Jump to" link.
- Continue past the We'll help you change (amend) your return screen.
- On the following screen, Have you already filed this return? select the first option (Yes) and then select I need to amend my 2018 return. Click Continue and then carefully follow the onscreen instructions to amend.
- Don't worry if your refund meter drops to 0; this is normal. Your calculations will come out correctly in the end.
- When finished, provide instructions for mailing your amended return, as amendments cannot be e-filed.
3 weeks after mailing your amended federal return, you can start tracking it at the IRS Where's My Amended Return? site. Allow at least 16 weeks for the IRS to process your amended return.
Processing times for amended state returns vary from state to state. If it's been more than 12 weeks since you mailed your amended state return, and you haven't heard anything, we suggest you contact your state tax agency.