BasisDiff produces reconciliation workpapers that explain each gap between a broker's 1099-DA, exchange statements, and your cost-basis software — so the return goes out the door with an answer, not a guess.
Starting with tax year 2025, brokers file Form 1099-DA reporting gross proceeds. For tax year 2026 they report cost basis too. Meanwhile Rev. Proc. 2024-28 ended universal per-wallet basis tracking. The result: preparers are seeing numbers that refuse to reconcile — and the IRS sees the same 1099-DA your client's software disagrees with.
The 1099-DA from the custodial broker rarely equals the "proceeds" line in Koinly / CoinTracker / CoinLedger exports. Different trade-pair handling, unit precision, and transfer classification.
After Rev. Proc. 2024-28, lots must be tracked per account and per wallet. Generic pools produce defensible-looking totals that don't survive a close look.
Notice 2026-20 transition relief runs only through December 31, 2026. Positions taken this season should be built to survive without it.
Three steps. The tool tier runs entirely in your browser — your transaction files never leave your machine.
Your cost-basis software CSV and the broker's 1099-DA / exchange statement. The page works offline — turn on airplane mode and it still runs.
Every unmatched dollar is classified: missing lots, wallet-transfer miscounts, unit and price-feed deltas, unpriced assets, pair mismatches — with the rule reference for each class.
A difference ledger (CSV + summary PDF) you can attach to the client file: what differs, why, by how much, and what source supports each side.
"We don't upload your data" is a claim. These are verifiable mechanisms:
The computation page ships with a strict Content-Security-Policy (connect-src 'none'). Your browser physically refuses any outbound request while the tool runs.
Download the single-file version, disconnect entirely, open it from disk — it produces the same report. Try it on the pilot.
Only for the human-reviewed tier do you send us files. They are deleted after delivery — stated in writing on every engagement.
Self-serve tooling and reviewed workpapers, priced for one-off client work.
| Tier | What you get | Price |
|---|---|---|
| Pilot report3 slots — free | One client file reconciled by us, delivered as the full difference ledger + summary. You keep the workpapers either way. In exchange: your feedback on what the report is missing. | $0limited time |
| Reviewed reconciliation | Human-reviewed difference attribution for one client-year: ledger, per-class totals, source references, open-items list. | $199–299per report |
| Self-serve toolpilot build | The browser-side reconciliation engine. Runs offline, nothing uploaded. Try it now → | $29+per tax year |
BasisDiff provides data reconciliation software and workpapers. It does not provide tax, legal, or investment advice, and nothing in a report constitutes a determination of tax liability.
No. We reconcile datasets and attribute differences to causes with source references. Interpretation and filing decisions stay with you or your CPA/EA. This boundary is part of the product, not a footnote.
Exports from Koinly, CoinTracker and CoinLedger, custodial broker 1099-DA forms, and exchange statements. If your source isn't listed, mention it in the pilot request — source coverage is exactly what the pilot phase is for.
Tool tier: there is nothing to keep — computation happens in your browser and no file is transmitted. Reviewed tier: files are used to produce your report and deleted after delivery.
Because the broker files the 1099-DA with the IRS independently. If the two disagree, the discrepancy exists whether or not you look at it. A reconciliation ledger documents why the difference is there — which is cheaper to produce now than to explain later.
Then the ledger says so. Unresolvable classes are listed as open items with the evidence available — a documented open item is materially better than an undocumented one.
We're onboarding the first three preparers at no cost. You get a complete reconciliation workpaper for one client; we get ground truth on what the report must contain.
Request the pilotA short form — no file upload, no account.