If it is already reported on your tax return, you do not need to amend to add.  

As a shareholder or partner, the K-1 is issued to you to report your portion of income and deductions.  The 1099-B transaction will generate either a long term or short term capital gain or loss. The net gain or loss will show on line 7 of your Form 1040 along with a Schedule D and Form 8949.  

Another way to verify is to enter the Schedule K-1 to see if the result creates any differences in the refund or tax due.  Steps to amend in TurboTax

In amendment,

• At the right upper corner, in the search box , type in K1 and Enter 
• Select the 1st choice on the search results - Jump to K1
• Follow prompts

This is for a stock I both purchased and sold in 2020 of a partnership. Is the K-1 I was sent irrelevant then?

No, the K-1is not "irrelevant" because you bought and sold the partnership interest ("shares") in the same year.

You have two reasons to report the K-1 on your return:

1. The K-1 reports your share of the partnership's 2020 income/loss and deductions for the period you owned a partnership interest. 

2. The K-1 reports information used to calculate your basis in the partnership. You need that information to calculate your gain/loss on the sale of the interest.

The gain/loss is already captured on the 1099-B as I completely disposed of my stock. If I'm understanding correctly in this case I would not need to include the K-1 info since the gain/loss from the sale of this stock is already reporting on the 1099-B. Am I correct? Sorry if it seems like I'm beating a dead horse. I appreciate your input.

You may still need to  enter the K-1 to report your share of the partnership's current year income/loss and deductions (Boxes 1 through 20). That is separate from the gain/loss information on the 1099-B.

If your K-1 does not report anything in boxes 1-20, then you don't need to enter it in your tax return.

I received a K-1 for shares I bought and sold/tendered in 2014 or so.  After 9 years (and sometimes in between as well).. am i to report this

You likely are not able to amend your 2014 tax return.  

You have three years from the date that you filed your original tax return or two years after the date that you paid the tax on that tax return to amend or make changes.

Retain the form with your tax records should the questions arise.

See IRS Topic No. 308, Amended returns, here.

When to file

Generally, to claim a refund, you must file Form 1040-X within 3 years after the date you filed your original return or within 2 years after the date you paid the tax, whichever is later.

I received a K-1 after investing in Proshares UCO, SCO and BOIL in 2023.  All of these were on my 1099 but I also received a surprise K-1 in March after my taxes were completed.  Overall, I made about $15,000 on these 3 stocks last year.  Adding the K-1 increased my tax burden by over $2000.  Seems like double taxation to me but my accountant says it's legit!  Think twice about buying Proshares leveraged commodity ETF's.

I got a tax package for proshare ultra bloomberg natural gas (BOIL)  All that is included is a K-1 (1065) it has checked off Schedule K-3. I dont have a 1099 B and not sure where I get that from.  any help trying to report these would be helpful Thanks in advance!

IRS Schedule K-1 and K-3 may be filed with the Premium version of TurboTax Online or the Premier version or above of TurboTax Desktop.

In TurboTax Online Premium, report IRS Schedule K-1 by following these steps:

• Down the left side of the screen, click Federal.
• Down the left side of the screen, click Wages & Income.
• Scroll down to S-corps, Partnerships, and Trusts and click on the dropdown menu to the right.
• Click Start/Revisit to the right of Schedule K-1
• Select Partnerships/LLC's (Form 1065).

@cbsprings