Form 1099-DA field reference
Form 1099-DA Box 12a–12b: Transferred-in units and date
What to check
- Trace the sending wallet or broker
- Carry over original basis
- Do not use the transfer date as acquisition date
Where Box 12a–12b flows on your return
Boxes 12a-12b don't map to a Form 8949 line directly, but they explain why Box 1d (acquisition date) or Box 1g (basis) might be blank or unreliable for a transferred-in position — the receiving broker's own records only start at the transfer-in date shown here, not your true original purchase.
How Box 12a–12b works
Boxes 12a and 12b report the number of units transferred into the broker's custody and the date of that transfer, for digital assets that arrived in the account from an outside wallet or another broker rather than being purchased directly through this broker. This is distinct from an acquisition date — the transfer-in date only tells you when the units arrived at this custodian, not when you originally acquired them.
A receiving broker generally cannot independently verify what you originally paid for a transferred-in position unless the sending broker or exchange supplied a basis-transfer statement along with the transfer. When that information does not accompany the transfer, the receiving broker may report the position as if it had no known basis, leaving Boxes 1d and 1g blank on the eventual 1099-DA for that sale.
This is one of the most common sources of understated basis on digital-asset tax reporting: if you do not proactively supply your original cost basis and acquisition date to a new broker or reconstruct it from your own records before the eventual sale, the 1099-DA can imply zero or unknown basis for a position you actually paid real money for, overstating your taxable gain unless you correct it on Form 8949.
Worked example
Kai transfers 2 BTC from a self-custody wallet into an exchange account; the exchange records Box 12a as 2 units and Box 12b as the March transfer-in date. Kai originally bought that BTC 18 months earlier for $30,000. Because the exchange has no visibility into that original purchase, its 1099-DA leaves Box 1d and 1g blank when Kai eventually sells, so Kai uses personal purchase records to report the correct $30,000 basis and the true, longer holding period on Form 8949 rather than accepting an unknown-basis treatment.
Continue the filing flow
Frequently asked questions
Is the date in Box 12b the same as my acquisition date?
No — Box 12b only reports when the digital asset units arrived at this broker's custody, not when you originally acquired them. Your true acquisition date and cost basis need to come from your own records covering the period before the transfer.
Why does my 1099-DA show no basis for a position I transferred in from another wallet?
Unless the sending platform supplied a basis-transfer statement, the receiving broker generally has no way to know your original cost basis, so it may report the transferred-in position without a basis figure. You need to supply your own purchase records to report the correct basis on Form 8949.
What can I do to avoid understating my basis on a transferred position?
Keep your original purchase confirmations and, where possible, ask the sending platform or broker to include a basis-transfer statement with any outgoing transfer, since that is the main way basis information follows the asset between custodians.