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1099-DA Cost Basis Missing: What It Means and What to Do

Short answer: A blank cost basis on a Form 1099-DA does not mean your basis is zero, and it does not mean you owe tax on the full sale amount by default. It usually means the broker was not required to report your basis. The IRS says you must calculate basis yourself before you file ("You must calculate basis before you file your tax return").

Why your 1099-DA may show no basis

According to the IRS instructions for Form 1099-DA (2026), brokers must report basis only for covered securities. Basis is optional for noncovered securities. A noncovered digital asset includes:

• an asset acquired before 2026;
• an asset transferred in to the broker providing custody (see boxes 12a and 12b);
• an asset the broker did not hold in custody when you acquired it.

A broker that reports a noncovered sale may check box 9 ("Check if Digital Asset Is a Noncovered Security"). If box 9 is checked, the broker does not have to complete boxes 1d, 1g (cost or other basis), 1h, 1i, or 6, and does not have to check box 2.

The IRS Tax Tip noted in our research says most Forms 1099-DA for 2025 did not include basis. (We did not re-read that Tax Tip for this page; see "What we could not verify".)

Covered vs. noncovered, in plain English

How to find your own basis

Basis is the cost to acquire the asset, including transaction fees, commissions, transfer taxes and other acquisition costs (Form 8949 instructions). Places to look:

1. Exchange history: download your full transaction or trade history (CSV) from each exchange you used. Look for the buy that matches the units you sold.
2. Wallet and on-chain records: transfer dates, amounts and fees.
3. Bank or card statements: the dollar amount you paid.
4. Prior tax returns and prior Forms 1099-B, 1099-MISC, 1099-DA or software exports.
5. Records for assets you earned or received: the amount you included in income is generally the starting point for basis (see the IRS example in the Form 8949 instructions on services paid in digital assets).

If you sold only part of a position, identify which units you sold. Without adequate and timely identification, the broker generally reports the earliest units first, but that is the broker's reporting rule. Your return should reflect the correct facts and your own records.

Where it goes on Form 8949

For a transaction your 1099-DA shows without basis (or with basis not reported to the IRS):

• Check box H (short term) or box K (long term) on Form 8949.
• Column (d): proceeds shown in box 1f of the 1099-DA.
• Column (e): your correct basis from your own records.
• Column (g): usually leave blank; column (h): column (d) minus column (e).

Short term means held one year or less; long term means more than one year. Count starts the day after you acquired the asset.

Example (made-up numbers)

You bought 2 units of "ABC" in 2024 for $2,000 total, including fees. In 2026 you sold them on an exchange. The 1099-DA shows box 1f proceeds $5,000, box 1g blank, box 9 checked, code K.

• Form 8949, Part II, box K. Column (d) $5,000; column (e) $2,000 (your records); column (h) $3,000 long-term gain. Example only; it is not a statement about how any particular transaction is taxed.

What if you can't find records?

The IRS pages we read do not give a special method for rebuilding missing crypto basis. The Form 8949 instructions say that if you lost or did not keep records of basis, you can contact your broker for help. If records are incomplete, a qualified tax professional can advise on what reasonable evidence supports your position. Do not guess silently, and do not assume a basis of zero or a basis equal to proceeds without understanding the effect.

Keep your records

Keep exchange exports, wallet records, copies of each 1099-DA and any correspondence with the issuer. The IRS record-retention guidance says to keep records that support items on a return until the period of limitations for that return expires; the usual period is generally 3 years from filing, but longer periods can apply (6 years for substantial under-reporting; indefinitely if no return was filed).

FAQ

Is a blank basis the same as zero? No. Blank usually means the broker did not report it. Use your own records.

Do I need to wait for a corrected form? If the form is merely missing optional basis, there is nothing to correct. If the form has wrong information, the IRS says to request a corrected form from the issuer and not to wait to file. See 1099-DA wrong cost basis.

Which box on Form 8949 do I check? Box H or K when basis was not reported to the IRS; G or J when it was. See 1099-DA vs Form 8949.

I moved coins between exchanges. Is that why basis is missing? Often yes; see 1099-DA after transferring crypto between exchanges.

What if I got no 1099-DA at all? You still must report. The IRS says to report all income, gains and losses from digital asset transactions whether or not you receive a form.

What we could not verify

• Whether a given broker reports basis voluntarily for noncovered assets (varies by broker).
• The IRS Tax Tip 2026-07 statement about 2025 forms was taken from research notes, not re-read for this page.
• The exact methods the IRS would accept for undocumented basis (not found on the pages read).

Sources

• IRS, Understanding your Form 1099-DA — https://www.irs.gov/businesses/understanding-your-form-1099-da (page updated June 28, 2026; read October 17, 2026)
• IRS, Instructions for Form 1099-DA (2026) — https://www.irs.gov/instructions/i1099da (read October 17, 2026)
• IRS, Instructions for Form 8949 (2025 revision) — https://www.irs.gov/instructions/i8949 (read October 17, 2026)
• IRS, How long should I keep records? — https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records (read October 17, 2026)

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Not tax advice. Examples use made-up figures. Nothing here has been reviewed by a tax professional. We may earn commissions from affiliate links where marked; see the disclosure.