My Coinbase 1099-DA shows $0 or blank cost basis. Do I owe tax on the entire sale?

No. A blank or zero basis box means Coinbase did not know what you paid, usually because the crypto was transferred in from another exchange or wallet. You report your actual cost basis on Form 8949 and pay tax only on the real gain. The form's blank box is a reporting gap, not a verdict.

Why doesn't Coinbase know my cost basis?

Brokers only track basis for assets acquired inside their own platform, and mandatory broker basis reporting on Form 1099-DA applies only to covered assets acquired on or after January 1, 2026. Anything you bought elsewhere and transferred in, or bought before that date, generally shows proceeds without basis.

What records prove my cost basis to the IRS?

Trade confirmations and CSV exports from the exchange where you originally bought the coins, bank statements showing the fiat purchase, blockchain transaction hashes linking the transfer to your Coinbase account, and old 1099s or tax software reports. Together they show what you paid, when, and that the same units ended up on Coinbase.

How do I fix the missing basis on my tax return?

You do not amend the 1099-DA itself. You report the sale on Form 8949 with the proceeds from the form and the cost basis from your own records, using the appropriate box for transactions where basis was not reported to the IRS. The gain or loss then flows to Schedule D.

What is the per-wallet basis rule and why does it matter here?

As of January 1, 2025, the IRS eliminated universal basis pooling. Each wallet or account tracks its own basis and acquisition dates, with Rev. Proc. 2024-28 providing a one-time safe harbor to allocate existing basis across wallets. When you substantiate basis for coins sold on Coinbase, the records must tie to the units in that account, not to your holdings in general.

When should I hire a crypto tax professional instead of doing this myself?

Consider help if the amounts are large, records from a defunct exchange are missing, you have hundreds of transfers across many wallets, you missed the Rev. Proc. 2024-28 allocation, or you already filed using zero basis and overpaid. A CPA or enrolled agent experienced with digital assets can reconstruct basis and amend prior returns.

Coinbase 1099-DA Missing Cost Basis: What to Do

You opened your Coinbase tax documents, saw a sale reported with a blank or $0 basis, and did the math: if the IRS thinks you paid nothing, the entire sale is profit. Take a breath. A 1099-DA missing cost basis is one of the most common and most misunderstood situations in the first years of this brand-new form, and it almost never means you owe tax on the full amount. It means Coinbase does not know what you paid, and the job of proving it falls to you. That job is very doable.

This article is general information, not tax advice. Rules change and individual situations differ.

What Form 1099-DA is, and why it is new

Form 1099-DA, Digital Asset Proceeds From Broker Transactions, is the IRS information return that crypto brokers now file when you sell or exchange digital assets. It comes out of the final broker reporting regulations issued under the 2021 infrastructure law, and tax year 2025 was the first year it existed. If you sold crypto on Coinbase during 2025, the first 1099-DA you ever received arrived in early 2026 for that filing season.

The critical detail most panicked filers miss is that the form is being phased in. Brokers did not start reporting everything at once:

Tax year	What brokers report on Form 1099-DA
2025 (forms issued early 2026)	Gross proceeds only. The cost basis box is generally blank for everyone.
2026 and later	Gross proceeds on all sales, plus cost basis, but only for “covered” assets acquired on or after January 1, 2026 in that broker’s custodial account.
Transfers in, any year	Proceeds when sold; basis is typically blank because the broker never saw your purchase.

So a missing basis is not a glitch and not an accusation. For 2025 sales it is the default for every single customer, because the regulations only required brokers to report gross proceeds that year. Even after basis reporting begins, it applies to a narrow slice of assets. The IRS knows this. The system is designed around the assumption that many taxpayers will supply their own basis.

Why your basis is missing: the transfer-in problem

Coinbase can only report what it witnessed. If you bought 0.5 BTC directly on Coinbase, the platform has the purchase record and, for covered assets going forward, can report basis. But crypto that arrived at Coinbase from somewhere else is a black box:

Coins bought on Kraken, Binance.US, Gemini, or a defunct exchange and later withdrawn to Coinbase.
Coins moved in from a self-custody wallet such as a Ledger or MetaMask.
Coins received as gifts, payments, mining, or staking rewards elsewhere.

In all of these cases, Coinbase sees units appear at a deposit address with no price tag attached. When you sell them, the 1099-DA reports what you received (gross proceeds) and stays silent on what you paid. These transferred-in units are treated as noncovered, meaning the broker is not required to report basis on them at all, even after 2026.

This is the mirror image of a problem we covered in our guide to moving crypto to a Ledger cold wallet: the moment coins leave a platform, the platform loses the basis trail. Move them back onto an exchange later and the receiving exchange never had it. The transfer itself was not taxable, but it broke the paper chain, and you are the only party who can repair it.

What not to do: accept the zero and overpay

The worst response to a blank basis box is to shrug and report zero. If you bought ETH for $8,000 on another exchange, moved it to Coinbase, and sold it for $10,000, your real gain is $2,000. Report a zero basis and you are volunteering to pay tax on $10,000 of gain instead, roughly five times the correct amount in this example.

Nothing in the rules requires that. The 1099-DA is an information return, not your tax return. The IRS matches the proceeds figure to make sure you reported the sale; it does not assume the blank basis box is the truth about your costs. Your Form 8949 is where the real numbers go, and you are entitled to use your actual, documented basis.

The flip side matters too: do not invent a convenient number. An unsubstantiated basis is the one scenario where the IRS can push you toward zero. If you claim a basis you cannot back up with records, an examiner may disallow it, and then the full-proceeds nightmare becomes real. The goal is a documented basis, not an optimistic one.

How to substantiate your basis, step by step

Here is the practical workflow when your Coinbase 1099-DA shows proceeds with missing basis.

Identify which lots were sold. Match the sale on the 1099-DA to specific units: what asset, how much, and which deposit those units came from. Coinbase’s transaction history shows the incoming transfer date and amount.
Trace the units to their origin. Follow the transfer back to the source: the exchange where you bought them or the wallet that held them. The blockchain transaction hash (TxID) is your link between the sending address and your Coinbase deposit address.
Pull purchase records from the source. Export trade history CSVs, confirmations, and account statements from the original exchange while you still have access. Bank or card statements showing the fiat you spent are strong corroboration. If the source exchange is gone, old emails, screenshots, and prior tax software imports can fill gaps.
Establish the acquisition date. Basis determines the size of the gain; the acquisition date determines whether it is short-term or long-term. Both carry over through transfers, so document both.
Reconstruct value for non-purchase acquisitions. For mining, staking, or payment income, your basis is generally the fair market value when you received it, which you likely reported as income that year. Historical price data plus the receipt timestamp gets you there.
Report on Form 8949 with your real numbers. Sales where the broker did not report basis to the IRS go in the section of Form 8949 for that situation. Enter the proceeds from the 1099-DA and the basis from your records. If a form ever reports something you can show is wrong, Form 8949’s adjustment columns (with the appropriate code) let you correct it while staying reconciled to what the IRS received.
Archive everything. Keep the CSVs, hashes, and statements with your tax records. Substantiation only works if you can produce it years later.

Good crypto tax software automates much of steps 1 to 5 by ingesting API keys and wallet addresses, but the output is only as good as the accounts you connect. A missing exchange means missing basis in the software too.

The per-wallet rule change you cannot ignore

There is a structural change under all of this. Through 2024, many filers used a “universal” method that pooled all their holdings of a coin across every wallet and exchange when picking which units were sold. That option is gone. As of January 1, 2025, the IRS requires per-wallet, per-account basis tracking, and Rev. Proc. 2024-28 provided a one-time safe harbor for allocating your existing unused basis across wallets as of that date.

Practically, this means the basis you substantiate must belong to the units in your Coinbase account, not to your cheapest purchase anywhere. If you allocated basis under the safe harbor, your Coinbase lots already have defined basis and dates; use those. If you never did a formal allocation and hold coins across multiple venues, sorting that out is a priority, ideally with professional help, because every future sale depends on it.

The per-wallet rule also changes small everyday decisions. Even conversions inside Coinbase are disposals of specific lots now, which is why we walk through the lot mechanics in our comparison of Coinbase Convert versus selling and rebuying.

Covered vs. uncovered: what Coinbase will and will not report

Going forward, two categories define what shows up in the basis box:

Covered assets: acquired on or after January 1, 2026, in your Coinbase custodial account. Coinbase must report both gross proceeds and basis when you sell them.
Noncovered assets: acquired before 2026, or transferred into Coinbase from outside at any time. Coinbase reports proceeds; basis reporting is optional at best, and for transfers essentially impossible.

Buy and sell entirely within Coinbase after 2025 and this problem gradually disappears for those lots. But every long-term holder with pre-2026 coins, and everyone who practices self-custody, will keep seeing blank basis boxes for years. That is not a bug; it is the permanent shape of the system. Your records are the other half of the reporting regime.

When to hire help

Most people with a handful of transfers and intact records can handle this with software and patience. Bring in a CPA or enrolled agent who genuinely works with digital assets when:

The dollar amounts are large enough that a basis mistake costs thousands.
Records are missing because an exchange shut down or you lost account access.
You have high transaction volume across many wallets, DeFi protocols, or chains.
You never performed a Rev. Proc. 2024-28 allocation and hold assets in multiple places.
You already filed a return using zero basis and want to amend to recover the overpayment.
You receive an IRS notice (such as a CP2000) proposing tax on full proceeds.

A good professional does two things: reconstructs defensible basis from imperfect records, and documents the method so the position holds up if questioned. That is worth real money in exactly the situations above.

Bottom line

A Coinbase 1099-DA with missing cost basis is expected behavior, not a tax bill on your entire sale. The form is new, brokers only reported gross proceeds for 2025, and basis reporting only ever covers assets acquired on the platform from 2026 onward. For everything else, you substantiate your own basis: trace the units, pull records from the source, report the real numbers on Form 8949, and keep per-wallet records going forward so this gets easier every year. For more on how transfers, conversions, and self-custody interact with the new reporting rules, browse our crypto guides.

This article is general information, not tax advice. Rules change and individual situations differ. For significant amounts or messy records, consult a qualified tax professional.