CEX vs DEX: differences in tax treatment

Operations on centralized exchanges (Binance, Kraken…) and decentralized exchanges (Uniswap, 1inch…) have the same substantial tax treatment, but differ in important practical aspects.

Tax treatment: identical

In both CEX and DEX, a crypto sale is a capital transfer that generates a gain or loss. An ETH→USDC swap on Uniswap has exactly the same treatment as the same swap on Binance: a taxable event at the time of the exchange.

The technology executing the exchange (centralized order book vs smart contract) does not change the economic nature of the operation.

Relevant practical differences

Reporting to the AEAT (Forms 172/173)

• CEX based in Spain (Bit2Me, 2gether…): required to report balances and operations to the AEAT.
• Foreign CEXs (Binance, Kraken…): will report via DAC8 starting in 2026.
• DEX (Uniswap, Curve…): do not report directly to the AEAT. The information is on the public blockchain, but there is no automatic reporting yet.

Custody

• CEX: Assets are under the exchange's custody (risk of bankruptcy, hack…). You still report them.
• DEX: You control your private keys. No one provides custody for you.

History extraction

• CEX: You export a CSV with the entire history in a few clicks.
• DEX: You need to use blockchain explorers (Etherscan, etc.) or wallet analysis tools (Debank, Zapper, Koinly, Rotki…) to reconstruct the history.

Fees

• CEX: Trading fee charged by the exchange (included in the statement).
• DEX: Network gas fees (Ethereum, etc.) plus protocol fee. Gas fees are part of the operation cost and affect the cost basis.

Gas fees and the cost basis

In DEX operations, gas fees paid in ETH are part of the transaction cost:

• When buying: the gas paid is added to the acquisition cost of the purchased asset.
• When selling/swapping: the gas paid reduces the net disposal value.

In CEXs, trading fees are already detailed in the CSV and are treated the same way.

DEX and privacy: do not be confused

Using a DEX does not make operations invisible to the tax authorities. The blockchain is public. If your wallet is associated with your identity (because you deposited from a verified CEX), the AEAT can trace the operations.

Conclusion

Fiscally, CEX and DEX are the same. The difference is practical: CEXs provide the history in CSV; DEXs require more manual work. For a correct tax return, the origin of the operations does not matter; what matters is that all of them are correctly recorded and calculated.