Biggest DeFi Hacks and Their Tax Implications

DeFi hacks have cost users billions. If you lost funds in a hack, you might be wondering about the defi tax consequences. The good news is that theft losses may be deductible on your taxes, reducing your overall liability. This article covers the biggest DeFi hacks and how to handle them for tax purposes.

Major DeFi Hacks and Their Impact

DeFi platforms have been targets for hackers since the space exploded. The most notable hacks include the Ronin Network hack ($620 million), the Poly Network hack ($611 million), and the Wormhole bridge hack ($326 million). More recently, the Bybit hack in 2025 saw over $1.5 billion stolen. These events highlight the risks of decentralized finance.

How DeFi Hacks Affect Your Defi Tax Obligations

When you lose crypto to a hack, the IRS and many other tax authorities consider it a theft loss. In the US, theft losses are deductible as itemized deductions, but only if you itemize. The loss is calculated as the fair market value of the stolen crypto at the time of the theft, minus any insurance reimbursement. You must also reduce the loss by 10% of your adjusted gross income. For example, if you lost $10,000 and your AGI is $50,000, your deduction is $10,000 minus $5,000, or $5,000.

Tax Treatment of Stolen Crypto

The IRS treats stolen crypto similarly to other theft losses. You can claim the loss in the year the theft was discovered. However, you need to prove the theft occurred, such as with a police report or blockchain transaction records. For non-US taxpayers, rules vary. In the UK, for example, theft losses may be treated as capital losses, which can offset capital gains. Consult a local tax professional.

How to Report a DeFi Hack on Your Taxes

To report a theft loss, you typically use Form 4684 in the US. This form calculates the loss and carries it to Schedule A. You will need details like the date of discovery, the fair market value at the time of theft, and your cost basis. If the stolen crypto was held as an investment, the loss is a capital loss, which can offset capital gains. If it was held for personal use, it is a personal theft loss, which is more limited.

Preventing Future Hacks and Tax Headaches

While you cannot always prevent hacks, you can protect yourself by using hardware wallets, avoiding unaudited protocols, and diversifying across platforms. For tax purposes, keep detailed records of all transactions, including dates, values, and any losses. Tools like CryptaTax can help you track your portfolio and generate tax reports, making it easier to claim losses.

Illustrative Scenario

To illustrate how this applies in practice, consider the following scenario: Sarah, a crypto trader in the US, lost $20,000 in the Bybit hack. She discovered the theft in 2025. Her cost basis for the stolen crypto was $15,000. She files her taxes using CryptaTax, which helps her report the theft loss on Form 4684. After applying the 10% AGI floor (her AGI is $80,000), she deducts $12,000, reducing her tax bill.

Source: Koinly Blog