An accidental three-letter typo—BTC instead of KRW—on a South Korean crypto exchange created a $40 billion problem, and with it, a masterclass in cryptocurrency tax law. When you mistakenly receive crypto, the IRS may consider it taxable income under the "claim of right" doctrine, creating a liability even if you have to return the funds later.

On February 6, 2026, as reported, crypto exchange Bithumb intended to distribute small promotional rewards in Korean won (KRW). Instead, due to a simple data entry error, it credited hundreds of users with massive amounts of Bitcoin. This incident, while extreme, highlights a critical question for every crypto investor: what are the tax consequences of receiving cryptocurrency by mistake? Understanding the rules can save you from a massive and unexpected tax bill.

The $40 Billion Typo: What Happened at Bithumb?

What was meant to be a minor user engagement campaign quickly spiraled into one of the largest operational failures in the history of digital assets. According to reports from cryptoimpacthub.com and Bloomberg, the Bithumb incident unfolded with shocking speed.

The Promotion: Bithumb ran a "Random Box" event where users could win small prizes, intended to be between 2,000 and 50,000 KRW (roughly $1.40 to $35).
The Error: An employee configuring the payout mistakenly selected "BTC" as the currency unit instead of "KRW." A 2,000 KRW prize became 2,000 BTC.
The Result: Approximately 695 users were reportedly erroneously credited with a total of around 620,000 BTC, valued at over $40 billion at the time (as of February 2026 news reports), as detailed by mexc.com. For a few minutes, hundreds of ordinary users were paper billionaires.
The Chaos: Some users immediately began selling their newfound fortunes. This panic selling caused Bitcoin's price on Bithumb reportedly flash crashed by approximately 17%, creating a massive price difference between the exchange and the global market.
The Response: Bithumb detected the error within minutes, freezing trading, withdrawals, and all affected accounts.

Crucially, this was not a hack or an on-chain transaction of 620,000 real Bitcoin. It was an internal ledger error—the exchange's database showed balances that weren't backed by actual reserves. However, because users could trade these "ghost balances," the financial and tax implications became very real.

Is a Mistaken Crypto Deposit Taxable Income in the US?

For US taxpayers, the key to understanding the tax treatment of a mistaken deposit lies in a long-standing legal principle known as the claim of right doctrine.

The IRS and US courts have long held that if a taxpayer receives income under a "claim of right" and without restriction as to its use, it must be included in their gross income for the year of receipt. This holds true even if it is later discovered that the taxpayer was not entitled to the funds and must repay them.

How does this apply to the Bithumb incident?

Receipt of Property: The IRS treats digital assets as property for federal income tax purposes, as clarified in its guidance (irs.gov). When the users saw BTC in their accounts, they had received property.
Unrestricted Use: For a brief period, the affected Bithumb users had unrestricted access to the Bitcoin. They could sell it, trade it, or attempt to withdraw it. The fact that some successfully sold their holdings demonstrates this lack of restriction.
Inclusion in Income: Because the users received property (BTC) and had unrestricted control over it, the claim of right doctrine suggests the fair market value (FMV) of the Bitcoin at the moment of receipt constitutes taxable ordinary income.

If a user received 10 BTC when the price was $66,000, they would have to recognize $660,000 in ordinary income for that tax year, regardless of what happened next. This creates an immediate and significant tax liability.

Calculating Your Tax Bill on Mistakenly Received Crypto

A mistaken crypto deposit can trigger two distinct taxable events: the initial receipt and the subsequent disposal.

Event 1: The Receipt (Ordinary Income)

When you gain control over the mistaken deposit, you must determine its FMV in US dollars at that exact time. This amount is reported as "Other Income" on Schedule 1 of your Form 1040. It is taxed at your standard ordinary income tax rates.

This FMV also establishes your cost basis in the newly acquired crypto.

Event 2: The Disposal (Capital Gain or Loss)

If you sell, trade, or spend the mistakenly received crypto, you trigger a second taxable event. The tax outcome depends on the difference between the sale price and your cost basis (the FMV when you received it).

Capital Gain: If you sell the crypto for more than its value at receipt, you have a capital gain.
Capital Loss: If you sell it for less, you have a capital loss.

The holding period determines the tax rate. Since these events happen quickly, any gain or loss would almost certainly be short-term, meaning it's taxed at the same rates as your ordinary income.

Scenario	Received 1 BTC (FMV $65,000)	Sold 1 BTC 30 Mins Later	Taxable Event 1 (Ordinary Income)	Taxable Event 2 (Capital Gain/Loss)
A: Price Increases	Cost Basis = $65,000	Sale Price = $66,000	$65,000 Ordinary Income	$1,000 Short-Term Capital Gain
B: Price Decreases	Cost Basis = $65,000	Sale Price = $55,000	$65,000 Ordinary Income	($10,000) Short-Term Capital Loss
C: No Sale (Clawed Back)	Cost Basis = $65,000	N/A (Funds Reversed)	$65,000 Ordinary Income	No Capital Gain/Loss Event

As the table shows, even if you suffer a capital loss from panic selling during a flash crash, you are still on the hook for the ordinary income tax from the initial receipt. This is the tax trap that makes these situations so dangerous. Manually tracking the exact FMV at the moment of an unexpected deposit is nearly impossible, which is why a dedicated crypto tax platform is essential. Tools like dTax can automatically import your transaction history and use precise pricing data to establish the correct basis for every asset you receive.

Repaying the Funds: How IRC Section 1341 Can Help

So, you've reported the income and paid the tax. But the exchange demands the crypto back. Now what? You're out the tax money and the crypto.

Fortunately, the Internal Revenue Code provides a remedy for this exact situation: IRC Section 1341, Repayments.

This rule is designed to provide relief to taxpayers who, having included income under a claim of right, are forced to repay it in a subsequent tax year.

Conditions for Section 1341 Relief

To qualify, you must meet several conditions:

You included the item in your gross income in a prior tax year because it appeared you had an unrestricted right to it.
You are eligible for a deduction in the current year because it was established you did not have an unrestricted right to that income.
The amount of the repayment deduction is more than $3,000.

If you meet these conditions, you can recalculate your tax for the repayment year in two ways and choose the one that benefits you most:

Method 1: Simple Deduction: Calculate your tax for the current year, taking a deduction for the amount you repaid.
Method 2: Recalculate and Credit: Calculate your tax for the current year without the deduction. Then, determine how much your tax in the prior year would have decreased if the mistaken income had never been included. You take this amount as a credit against your current year's tax.

For Bithumb users, this means if they reported the income on their 2026 tax return and were forced to repay Bithumb in 2027, they could use Section 1341 on their 2027 return to either deduct the repayment or claim a credit for the taxes paid in 2026.

Key Takeaways for Investors After the Bithumb Incident

The Bithumb fiasco is a powerful reminder of the unique risks and complexities of the digital asset ecosystem. Here are the key lessons for every investor.

1. Impeccable Record-Keeping is Non-Negotiable

In a situation like this, data is your best defense. You must be able to prove the exact time of receipt, the FMV at that moment, the time of sale, and the proceeds. Keep copies of all communications from the exchange. Without this data, you cannot accurately calculate your income or defend your position to the IRS.

2. "Free Money" Is a Tax Trap

Never assume an unexpected windfall is free. The claim of right doctrine creates an immediate tax liability. Acting rashly by selling or moving the funds can compound the problem by creating a second taxable event. Your first calls should be to the exchange to report the error and to a qualified tax professional to plan your next steps.

3. Understand the New Broker Reporting Rules

Beginning with the 2025 tax year, crypto exchanges serving US customers will be required to issue Form 1099-DA. These forms will report gross proceeds from digital asset sales to you and the IRS. This increased transparency means the IRS will have a record of your transactions. If an exchange reports a large sale from a mistaken deposit, you must have the records to explain the corresponding basis and any subsequent repayment. The IRS has provided guidance in Rev. Proc. 2024-28 (effective January 1, 2025) (irs.gov) on how taxpayers can establish basis ahead of these new rules, highlighting the importance of getting your records in order now.

4. Automate Your Tax Compliance

The Bithumb incident demonstrates the sheer complexity of crypto tax calculations. A single mistaken deposit can involve ordinary income, capital gains or losses, and potential multi-year tax adjustments under Section 1341. Using a crypto tax software platform is the only scalable way to manage this.

By connecting your exchange accounts via API, a platform like dTax can provide a complete and accurate picture of your transaction history. It automatically calculates your cost basis, gains, and losses, and generates the necessary tax reports, saving you from a nightmare of manual spreadsheet work. Start automating your crypto taxes with dTax.

Frequently Asked Questions (FAQ)

What if I receive mistaken crypto but don't sell it before it's clawed back by the exchange?

Even if you don't sell, the claim of right doctrine likely still applies, meaning the fair market value at the time of receipt is considered ordinary income. If the funds are clawed back within the same tax year, you and your tax advisor may be able to argue that the transaction was nullified and no income should be recognized. If the clawback occurs in a subsequent tax year, you would report the income in the year of receipt and then seek relief under IRC Section 1341 in the year of repayment. This is a complex area that requires professional guidance.

Does this tax treatment apply to other mistaken deposits, like airdrops sent to the wrong address?

The underlying principle—gaining dominion and control over an asset—is broadly applicable. If a valuable airdrop is sent to a wallet you control, its fair market value is generally considered income upon receipt. The Bithumb case is unique because it was an internal exchange error creating "ghost balances," but the tax consequence stems from the user's temporary, unrestricted ability to control and trade those balances. The specific facts and circumstances of any mistaken deposit are critical.

How do the new broker reporting rules affect situations like this?

Starting with the 2025 tax year, exchanges will issue Form 1099-DA, reporting your digital asset transactions to the IRS. A mistaken deposit that is subsequently sold would likely appear as gross proceeds on this form. Without proper records to establish your cost basis (the FMV at receipt), the IRS might assume a basis of zero, drastically overstating your taxable gain. These new rules make it more important than ever to use a reliable system for tracking your crypto activity and ensuring your personal records match what the IRS receives from exchanges.