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1099-DA Shows the Wrong Cost Basis: What to Do

Short answer: Ask the issuer (the "Filer" named on the form) for a corrected 1099-DA. The IRS says: "Don't contact the IRS. We can't correct your Form 1099-DA." And "Don't wait to file your taxes." If you have no corrected form in time, Form 8949 has a way to report the correct basis.

1. Check first

Before assuming the broker is wrong, compare box 1g with your records:

• Lots and dates: did you sell the units you think you sold? Without adequate and timely identification, the broker generally reports the earliest units first.
• Fees: basis includes transaction fees and acquisition costs; proceeds in box 1f are net of transaction costs.
• Transfers in: units moved in from another wallet or exchange are noncovered, and the broker may treat them as acquired at the transfer date and time if it does not use your acquisition information (boxes 8, 12a, 12b). See transfers between exchanges.
• Gifts, inheritance or income assets: basis rules differ; the broker may not know the history.

2. Ask the issuer for a corrected form

• Find the Filer name and contact information at the top left of the form.
• Keep copies of the original form and all correspondence.
• Keep the corrected form with your records and report using the corrected form.

3. Why the IRS can't fix it

The form is issued by the broker; the IRS says it cannot correct it. Contacting the IRS is not the step the IRS asks you to take.

4. Don't wait to file

If a corrected form has not arrived, the IRS says not to wait. Report what is correct on your return with proper documentation (see step 5); a qualified professional can help with your specific situation.

5. Reporting a different basis on Form 8949

From the Form 8949 instructions (code B):

• If basis was NOT reported to the IRS (box H/K): enter your correct basis in column (e) and -0- in column (g).
• If basis WAS reported to the IRS (box G/J): enter the basis shown on the 1099-DA in column (e), even though it is wrong, enter code B in column (f), and correct it with an adjustment in column (g). Use the "Worksheet for Basis Adjustments in Column (g)": if the form's basis is larger than the correct basis, the adjustment is a positive number; if smaller, negative (in parentheses).
• If the type of gain (short vs long) is wrong: code T.
• If digital asset transaction costs are not reflected: code E with a negative adjustment in column (g).

Example (made-up numbers)

Proceeds (box 1f) $2,000. The 1099-DA shows basis $1,500 reported to the IRS (box G). Your records show correct basis $1,200.

• Column (d) $2,000; column (e) $1,500; code B; column (g) +$300 ($1,500 − $1,200); column (h) $2,000 − $1,500 + $300 = $800 (equals $2,000 − $1,200).

Reverse case: correct basis is $1,800: column (g) ($300); column (h) = $2,000 − $1,500 − $300 = $200.

If you use a different basis than the one reported, keep proof. Tax software may handle these adjustments differently; verify the result.

6. Keep proof

Keep exchange exports, wallet records, receipts, your calculation and the issuer correspondence for as long as the period of limitations for the return runs (generally 3 years from filing; longer in some cases).

FAQ

Can I fix it by calling the IRS? The IRS says it can't correct a 1099-DA.

What if the issuer refuses? The pages we read do not say; talk to a qualified professional.

What if the form shouldn't have been sent to me? Contact the issuer immediately, keep a copy of the form and correspondence, and don't wait to file.

Penalty risk? Not covered on the pages we read; ask a professional.

What we could not verify

• What happens if the issuer will not correct a form (not covered by the pages read).
• Any penalty or notice-handling details.
• The current-year Form 8949 text (we read the 2025-revision instructions).

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)

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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.