How to Reconcile a 1099-DA With the Wrong Cost Basis
Starting with tax year 2025, brokers file Form 1099-DA to report digital asset proceeds — and in many cases, cost basis. But broker-reported basis is often wrong. Tokens transferred from external wallets, received through hard forks, or acquired as gifts arrive with zero or unknown basis in the broker’s system. Here is how to fix it on your return without triggering an IRS mismatch.
Why Broker Basis Is Often Wrong
A broker can only report basis for assets it custodied from the original acquisition. When you transfer tokens from a self-custody wallet, another exchange, or a DeFi protocol to a broker, the broker has no record of what you paid. Under IRC §6045, brokers must report basis for “covered” assets — those acquired after the effective date in the broker’s custody. Assets that were non-covered (acquired before the tracking date or transferred in) show basis as zero or N/A.
Common scenarios where broker basis is wrong or missing:
- Wallet-to-exchange transfers: You bought ETH on Uniswap in 2022, held it in MetaMask, then transferred it to Coinbase in 2024 and sold in 2025. Coinbase’s 1099-DA shows the proceeds but has no basis — because it did not custody the asset at acquisition.
- Hard forks and airdrops: Forked tokens received as ordinary income at FMV (per Rev. Rul. 2019-24) have a cost basis equal to FMV at receipt. If the broker didn’t track the fork event, it may show basis as zero.
- Gifts: Gifted crypto carries the donor’s original basis (with a holding period carryover for long-term treatment). The broker has no way to know the donor’s basis.
- Staking rewards sold: Rewards received as ordinary income (per Rev. Rul. 2023-14) have a basis equal to FMV at receipt. If the broker issues a 1099-DA showing proceeds but zero basis for reward tokens, you are being taxed twice.
“The 1099-DA is a starting point, not the answer. Every sophisticated crypto holder should reconcile broker-reported basis against their own records before filing.”
— Saim Akif, CPA
Form 8949 Code B Adjustments: The Mechanics
When you report a sale on Form 8949, you select Box A, B, or C (or D, E, F for long-term) based on whether basis was reported to the IRS. For assets where the broker’s basis is wrong:
- Use Box B (short-term, basis not reported to IRS) or Box E (long-term) if the asset was non-covered or the broker did not report basis.
- Enter the correct basis in column (e) and the broker-reported basis (or zero) in column (g) as an adjustment.
- Use Adjustment Code B in column (f) to flag that the reported basis has been corrected. This tells the IRS that you are not ignoring the 1099-DA — you are correcting it with your own records.
If the broker reported a specific basis figure that is wrong (not just zero), you still use Code B and explain the discrepancy in your records. You do not need to attach a written explanation to the return, but you must have documentation ready if asked. Visit our 1099-DA Hub for a full Code B adjustment worksheet.
Documentation Requirements
To support a basis adjustment on Form 8949, you need:
- Proof of original acquisition: exchange confirmation, on-chain transaction hash, dated receipt
- FMV at acquisition date (from a reputable price source such as CoinMarketCap or the exchange’s trade history)
- Transfer records showing the asset moved from the original wallet/exchange to the selling broker
- For gifts: written statement from the donor with their original cost and date of acquisition (IRS recommends but does not require Form 709 documentation)
Saim’s practice retains all source documentation in a client file organized by wallet address and tax year. In an audit, the IRS can request records going back six years (or indefinitely for fraud). See our Audit Defense page for how we structure documentation packages.
What to File With Your Return
Your tax return must include:
- Form 8949 with each sale listed (or a substitute statement that conforms to Form 8949’s column requirements)
- Schedule D summarizing short- and long-term totals
- Any required Form 1099-DA attached as received (you do not need to file the 1099-DA separately; it is an information return sent directly to the IRS by the broker)
If you have hundreds or thousands of transactions, you may attach a CSV or PDF summary to Schedule D rather than listing each row — but the detail must be available on request. Use the 1099-DA Readiness Playbook to pre-organize your records before filing season.
Need Help?
A wrong 1099-DA basis can cost you thousands in over-reported tax. Saim Akif, CPA reconciles 1099-DA data against on-chain records and prepares Code B adjustments with full documentation. Schedule a 30-minute intake with Saim.
Frequently Asked Questions
What if my broker refuses to correct the 1099-DA?
Brokers are not required to issue corrected 1099-DAs simply because you disagree with the basis. You report the correct basis on Form 8949 using Code B regardless of what the broker does — and retain your documentation to support the adjustment if audited.
Does using a hardware wallet eliminate my 1099-DA obligation?
No. Your tax obligation exists regardless of whether a broker issues a 1099-DA. Self-custody assets are subject to the same tax rules — the absence of information reporting does not eliminate the tax. The IRS receives 1099-DA from the exchange you eventually sell through, even if you custodied the asset yourself for years.
What is the difference between “covered” and “non-covered” on a 1099-DA?
Covered assets are those where the broker tracked basis from the original acquisition in the broker’s custody. Non-covered assets have no broker-tracked basis — typically because the asset was acquired before the broker’s tracking date, transferred in from another wallet, or acquired through a non-tracked event like a fork. Non-covered sales use Box B or E on Form 8949.
How far back can the IRS go on a basis discrepancy?
Generally three years from the return due date, or six years if income is understated by more than 25%. For basis errors that compound across years (e.g., a wrong basis on a 2022 acquisition affects every subsequent year that lot is held), the IRS can reach back to the original basis error year.
Received a 1099-DA with incorrect cost basis? Saim reconciles every line against on-chain records and prepares the Form 8949 adjustments. Schedule a 30-minute intake with Saim.