How to fix missing cost basis on your 1099-DA

Last updated: 2026-10-21

Short answer: a blank cost basis usually means your coins were bought before 2026 or transferred in from another wallet, so the broker wasn't required to report basis. Your basis isn't zero. You report it yourself on Form 8949 using your own purchase records.

Why basis is missing (per the IRS Form 1099-DA instructions)

Brokers must report gross proceeds for all digital asset sales after 2025.
They must report basis only for covered securities: assets acquired after 2025 in the broker's custodial account and held there until sale.
Assets acquired before 2026, or transferred in, are noncovered. The broker can check box 9 and skip basis.
If you moved coins in, boxes 12a and 12b may show the units and transfer-in date.

How to fix it

Find the Form 8949 code on your 1099-DA (H or K means basis wasn't reported).
Rebuild basis from exchange history: buy dates, amounts, and fees for the units sold.
Import every exchange and wallet into one tracker so transfers carry their original basis. CoinLedger and Koinly both produce Form 8949.
Report the proceeds from the 1099-DA and your real basis on Form 8949 and Schedule D. See our Form 8949 guide.
Keep the records. If the IRS later sends a CP2000 based on zero basis, it's a proposed change you can answer with documentation (IRS letter help).

Software links are affiliate links; CoinLedger code CRYPTOTAX10 gives 10% off. Disclosure. This is general information, not tax advice.

Years of trades and no records? Firms in the directory offer cost basis reconstruction, for example Gordon Tax lists 1099-DA reconciliation.

Got a letter? Letter 6173 vs CP2000

FAQ

Why is box 1g blank on my 1099-DA?

Per the IRS instructions, brokers must report basis only for covered securities: assets acquired after 2025 in that broker's custodial account and kept there. Crypto bought before 2026 or transferred in is noncovered, and the broker may check box 9 and leave basis blank.

Does a blank basis mean my basis is zero?

No. The instructions tell brokers to enter -0- only if the asset actually had a basis of zero. You report your real basis on Form 8949.

Which Form 8949 box applies?

Your 1099-DA has a code: H (short-term, basis not reported to IRS), K (long-term, not reported), G and J when basis was reported, or Y if the holding period is unknown.