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posted Apr 9, 2025 12:20:25 PM

What do I report if Form 1099-B Box 1e (Cost or Other Basis) shows Unknown?

I purchased mutual funds years ago before Financial companies were required to track or provide Cost Basis to their customers. How do I establish cost basis in this situation?

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1 Replies
Expert Alumni
Apr 9, 2025 12:31:46 PM

There are cases when the issuer of the IRS form 1099-B does not have the cost basis information or is not required to report the cost basis information that they have.  

 

The cost basis for the mutual funds is the amount that you paid when you purchased the investment.

 

You may have to refer to your personal records including sales tickets to locate the information that is needed.

 

You may enter an IRS form 1099-B into TurboTax Premium Online on a One by one basis by following these steps.

 

  1. Down the left side of the screen, click Federal.
  2. Down the left side of the screen, click Wages & Income.
  3. Click the down arrow to the right of Investments and Savings.
  4. Click to the right of Stocks, Cryptocurrency, Mutual Funds, Bonds, Other (1099-B).
  5. Click Add investments.
  6. On the Let's import your tax info screen, select Enter a different way.
  7. On the OK, let's start with one investment type screen, select Stocks, Bonds, Mutual Funds, then Continue.
  8. At the screen Which bank or brokerage, enter the information.  Click Continue.
  9. Do these sales include any employee stock, enter No.
  10. Do you have more than three sales, enter No.
  11. Do these sales include any other types of investments, enter No.
  12. Did you buy every investment listed, enter Yes.  Continue.
  13. On the screen Now, choose how to enter your sales, select One by One.  Select Continue.
  14. At the screen Look for your sales on your 1099-B, select Continue.
  15. Enter the information.  Select The cost basis is incorrect or missing on my 1099-B.  Continue.
  16. At the screen We noticed there's an issue with your cost basis, select I know my cost basis and need to make an adjustment.  Continue.