Coinbase missing cost basis: tracing crypto you transferred in

Why Coinbase has no cost basis

According to Coinbase’s help article on cost basis, when you receive crypto from an external source, Coinbase does not have the original purchase price or acquisition date. Such assets are noncovered, as are assets acquired before January 1, 2026.

For noncovered sales, Coinbase reports the proceeds on Form 1099-DA and shows the cost basis section blank, with the noncovered box checked. In its Retail Tax Center, Coinbase estimates the gain or loss with a $0 cost basis. A blank basis means the record is elsewhere; it does not mean the crypto cost nothing.

The acquisition date Coinbase shows is a placeholder

For assets moved in from an external wallet, Coinbase records the date of receipt as the acquisition date for its own lot selection. Coinbase calls this a system placeholder and says to use the actual original purchase date when working out whether a gain is short-term or long-term.

So each deposit needs two things from the original records: what was paid, and when.

Trace each deposit back to its purchase

1. List the deposits. Date, asset, quantity, network, and transaction hash for every receive from an external source.
2. Find the sending side. Match each deposit to a withdrawal in another exchange or wallet by hash, amount, and time. See how to reconcile transfers between wallets.
3. Keep going until you reach a purchase. Crypto may have passed through several wallets before it reached Coinbase.
4. Split deposits that hold several purchases. One transfer can contain units bought on different dates at different prices; each purchase is a separate lot.
5. Record what you cannot find. A closed exchange or a missing year becomes an open item with the account, period, and what you checked.

Adding the details in Coinbase

Coinbase lets you add the date acquired and total cost basis for transfers on its Add transaction details page: open the Needs review tab, select the transaction, choose Add details, and use Split this transfer when one deposit holds several lots. The steps are in the same help article.

Entering a figure in Coinbase does not replace the evidence behind it. Keep the purchase record and the transfer that connects it to each deposit. Coinbase also notes that for noncovered assets you can give your tax preparer reports or statements from the exchanges and wallets where you obtained the crypto.

Demo: one deposit, two purchases

The deposit is split into two lots with their real purchase dates and costs, not the March 2026 placeholder. The note keeps both hashes and the two trade records together for your preparer.

What to keep for your preparer

• The Coinbase Form 1099-DA and the detailed Coinbase transaction history.
• For each deposit: the sending-side export and the transaction hash.
• The original purchase records, with dates and amounts.
• A short note per deposit, and an open-items list for anything you could not trace.

When a cleanup review can help

If deposits came through several wallets or exchanges, or some accounts are closed, Elena’s transaction cleanup traces each deposit to its acquisition, splits lots, and documents the result for your preparer. Tax advice, return preparation, and filing are not included.

Coinbase is a trademark of its owner. This guide is independent and based on Coinbase’s public help article as of October 2026. It is not tax advice.

See how the records fit together

View the illustrative record package to compare source rows, a working ledger, correction notes, and an open-items list.

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