1099-B Unknown Term Code X (Basis Not Reported & Unknown)

carriskoul — Tue, 24 Feb 2026 03:21:12 GMT

I have a couple of these subject sales on my 1099-B.

1.) For one of them I know how to get the cost basis and know to check Box B.

Do I still need to add a code in column (f) after I enter the cost basis in column (e) or can I leave column (f) blank?

2.) For the others where the amounts are not that much and I'm not concerned about figuring out a cost basis, do I need to enter a code in column (f)? If so, do I enter an "X"?

Re: 1099-B Unknown Term Code X (Basis Not Reported & Unknown)

MonikaK1 — Sat, 11 Mar 2023 16:33:41 GMT

According to IRS Instructions for Form 1099-B, if you received a Form 1099-B (or substitute statement) for a transaction, box 2 may help you determine whether your gain (or loss) is short term or long term or subject to special rules. If box 2 is blank and code X is in the "Applicable checkbox on Form 8949" box near the top of Form 1099-B, your broker doesn't know whether your gain (or loss) is short term or long term. Use your own records to determine whether your gain (or loss) is short term or long term.

The code X is really for your information. Enter the cost basis and purchase date to produce a valid non-covered code for the holding period. See this thread for another discussion of this issue.

Enter as much of the information from Form 1099-B as is practical in TurboTax. The IRS matching programs will be looking for the amounts and sources of the sales proceeds.

See this tax tips article for more information from TurboTax regarding Form 1099-B.

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1099-B Unknown Term Code X (Basis Not Reported & Unknown)

Re: 1099-B Unknown Term Code X (Basis Not Reported & Unknown)