Check your 1099-DA against your own cost basis

Your broker's new form reports your proceeds — but the cost basis on it is often missing or wrong. Line up each sale on the form against your own records and see both gains before you file.

Reconcile your 1099-DA, sale by sale

All math runs in your browser; nothing is uploaded. A draft of your rows is saved only in this browser (localStorage) so you can come back to it.

Import summary rows from a CSV (optional)

Have your sales in a spreadsheet or an exchange export? Save a summary CSV — one row per sale — and import it here instead of typing. Columns are matched by header name (asset, proceeds, cost basis on the form, your cost basis, date acquired, date sold). The file is read in your browser only; nothing is uploaded.

Choose a CSV file

…or paste CSV rows

Before you file: the reconciliation checklist

Keep your exchange CSV exports. Download the full transaction history from every exchange you used — it is the evidence behind your own basis figures.
Keep wallet-to-wallet transfer records. Transfers between your own wallets are not sales; records showing the same asset leaving one wallet and arriving at another are how you prove a missing basis is real.
Document your cost-basis method. Write down whether you used FIFO, HIFO, or specific identification — and use that same method consistently across the whole return.

If you have many exchanges → compare software Estimate federal tax on this gain → calculator

Educational estimate only — not tax, legal, or accounting advice. CryptoTaxAI does not file with the IRS and does not replace Form 8949, Schedule D, or a qualified tax professional. Verify figures against your records and current IRS publications. Educational only — not tax advice.

Why the basis on your form can be wrong

Form 1099-DA is new, and brokers only report cost basis for covered assets — broadly, assets they have held since purchase. If you transferred coins into an exchange from a wallet or another platform, the broker sees the sale but never saw the buy, so the basis box is blank or missing entirely. The IRS instructions for Form 1099-DA are explicit that brokers report what they know; filling the gap is the filer's job. Our 1099-DA basis reporting guide explains the covered/noncovered timeline in full.

The risk is asymmetric. Report the form's proceeds with no basis and the gain is computed as if the coins cost you nothing — you overpay. Report your own lower gain without records and an IRS matching notice asks questions. The reconciler above shows you the size of that gap, sale by sale, while there is still time to gather the records that close it.

How the comparison works

Gain using the form's basis = proceeds minus the basis printed on your 1099-DA. Where the form reports no basis, this tool uses $0 — the treatment you would effectively get if the form were taken at face value.
Gain using your basis = proceeds minus the basis from your own records: exchange histories, wallet logs, and earlier purchase confirmations.
Difference = the first gain minus the second. A positive difference is tax you would overpay by filing the form's numbers uncorrected.
Short/long-term split: add both dates to a row and the tool classifies the holding period (365 days or less is short-term) and splits your total gain accordingly.

What to do with a difference

You still report every sale on Form 8949 — with your correct basis, and the adjustment codes the form provides where the broker's figures differ. If the gap comes from transfers, assemble the transfer records now, while exchange histories are still downloadable. If you have sales across many exchanges and the rows above keep growing, that is the point where crypto tax software earns its price: it imports every lot and keeps the audit trail for you. Not sure which side of that line you are on? Take the two-minute software quiz.

Common questions

That is common for assets you transferred into the broker: the broker never saw your purchase, so it reports proceeds only. It does not mean your basis is zero — you report your real basis from your own records on Form 8949. But if you filed using the form alone, the gain would be overstated, which is the exposure this tool shows.

No. It is an educational estimator that runs in your browser. It does not file, amend, or reconcile anything against IRS systems, and it is not a substitute for Form 8949.

Keep your exchange CSV exports, records of wallet-to-wallet transfers (which show assets moving, not being sold), and a note of the cost-basis method you used — FIFO, HIFO, or specific identification — applied consistently across your return.