What Happens If Your 1099-DA Cost Basis Looks Wrong?
Getting a tax form with a number that doesn’t match your own records is unsettling, especially when that form is new and the rules around it are still being understood broadly.
The short answer
Form 1099-DA reports digital asset transactions to the IRS, but if the cost basis a broker reports doesn’t match your own records, you’re generally still permitted to report the correct figure on your tax return, provided you can support it with documentation. A mismatch between the form and your own records isn’t automatically a problem; it’s a signal to review your records and, if needed, correct the figure when you file.
Why cost basis mismatches happen in the first place
Brokers can only report what they know, and if crypto was transferred into a platform from another wallet or exchange, the receiving broker may not have visibility into what was originally paid for it. In that situation, the broker may report a basis of zero, an estimated figure, or simply flag the basis as unknown, none of which necessarily reflects the actual amount paid. This is closely tied to the broader challenge of tracking crypto cost basis across multiple platforms and wallets, since crypto’s portability between accounts is exactly what makes broker-reported basis figures unreliable in a lot of common situations.
What to do when the numbers don’t match
- Gather supporting documentation. Purchase confirmations, wallet transaction histories, and records of transfers between platforms all help establish the actual cost basis.
- Report the accurate figure, not the form’s figure. Taxpayers are generally responsible for reporting correct information on their return, even when a broker-issued form shows something different.
- Keep the documentation on file. Supporting records should be retained in case the IRS later has questions about the discrepancy between the form and the return.
- Note the mismatch doesn’t need to be resolved with the broker first. A return can reflect the correct basis regardless of what a broker’s form shows, as long as records back it up.
Why this differs from more familiar tax forms
Forms like a W-2 or a traditional 1099 for interest income are usually complete and accurate because the issuer has full visibility into the transaction from beginning to end. Crypto’s nature, moving freely between wallets, exchanges, and platforms with no central ledger tying it all together, means a broker issuing a 1099-DA may simply be missing information that only the taxpayer has. This gap is one of the newer wrinkles introduced as crypto brokers ramp up standardized reporting, and it sits alongside other still-evolving areas like how gains are calculated for inherited crypto, where cost basis questions can be just as complicated for different reasons.
If a mismatch is discovered after filing
If a return has already been filed and a cost basis error is discovered afterward, amending the return with the corrected figure and supporting documentation is generally the appropriate path forward, rather than leaving the discrepancy unaddressed. Because rules around digital asset reporting are still developing and specific outcomes depend on individual circumstances, working with a tax professional familiar with how crypto is taxed is worth considering for anything beyond a straightforward correction.
The takeaway
A 1099-DA is a reporting tool, not necessarily a complete or final record of what actually happened with a given asset. When your own documentation tells a different, more accurate story than the form does, keeping thorough records and reporting the correct figure is the standard approach, not an exception to it.