1099-DA cost basis is the cost or other basis figure a digital asset broker reports on Form 1099-DA for units sold from a customer's account. It is the amount the broker recorded when the units were acquired in that account, including the transaction costs allocated to the purchase, and it is populated only when the units sold are covered digital assets.
A broker can only report the basis it knows. When a customer buys a digital asset at that broker, the broker records the price paid and the fees, and that record becomes the basis it reports when the same units are sold. When the units arrived by transfer, the broker has no purchase record and no basis to report. Broker-reported basis is therefore a statement about the broker's own books, not about what the units actually cost the taxpayer.
The form indicates whether basis was reported to the IRS. Where it was, the sale belongs in the box on Form 8949 for sales with basis reported; where it was not, the sale goes in the box for basis not reported and the taxpayer's own figure fills the column. The distinction between broker-reported basis and the taxpayer's cost basis is the whole reason a reconciliation exists.
Under Regulations section 1.6045-1 basis reporting applies to sales on or after January 1, 2026, and only for covered digital assets: units acquired in the customer's account at that broker on or after January 1, 2026. Sales in 2025 carry proceeds only. Sales in 2026 and later of units bought at the broker before 2026, or of transferred-in digital assets, are noncovered, and the broker is not required to report basis for them. A broker may report basis for a noncovered unit where it holds the information, and the form says whether it did.
The tax consequence is that a blank basis field changes who supplies the number, not whether basis exists. Every unit sold has a basis under section 1012, whether or not the broker reports it. For a noncovered sale the taxpayer establishes the basis from purchase records, the sending wallet's history or a reconstruction, and enters it on Form 8949. For a covered sale the broker's figure is the presumptive one, and if the taxpayer's records show it is wrong, Form 8949 provides an adjustment code for basis that was reported incorrectly rather than a licence to substitute a different number silently.
Broker basis also reflects the lot the broker treated as sold. If the customer gave no instruction, the broker's default ordering decides which units, and their basis, went out. That is a question of digital asset identification, and for covered units it has to be settled with the broker before the sale, not in the tax software afterwards.
An investor buys ETH on an exchange in November 2025 and sells it there in March 2026. The exchange knows exactly what was paid, but the units were acquired before January 1, 2026, so they are noncovered and the basis field is blank. The investor reads the blank as zero, or the software does, and the whole sale is reported as gain. The purchase sits in the exchange's own history and only needed to be carried across.
Read our 1099-DA accounting and cost basis reconciliation
CountDeFi reconciles broker-reported basis against your complete transaction history, including blank basis fields, pre-2026 purchases and lot identification. See pricing.
