1inch Network and DEX aggregators: taxation of each operation in Spain

#1inch and DEX aggregators: how to declare each swap fiscally

1inch is the most popular DEX aggregator: instead of swapping directly on Uniswap, Curve or SushiSwap, 1inch splits the swap between several protocols to get the best price for the user. This optimization creates additional tax complexity.

What is a DEX aggregator?

An aggregator is a smart router that:

1. Receive your order: you want to exchange 1 ETH for USDC.
2. Check prices on Uniswap v2, v3, Curve, SushiSwap, Balancer, etc.
3. Split the order: 60% in Uniswap v3, 30% in Curve, 10% in Balancer.
4. Execute everything in a single transaction.

The result: you get more USDC than if you had gone directly to a DEX.

Taxation of the swap in 1inch: one or multiple taxable events?

Although internally the aggregator divides the swap into parts, for the user it is a single on-chain transaction and a single taxable event:

• Input asset: ETH (value in EUR at the time of the swap).
• Output asset: USDC (value in EUR at the time of the swap).
• The difference = capital gain/loss.

You don't need to break down internal routing by Uniswap/Curve/Balancer: what matters is what came into and what came out of your wallet.

The 1INCH token: governance and utility

1inch has its own governance token (1INCH). It is used to vote on protocol parameters and can be locked to receive benefits from the protocol.

1INCH Taxation:

• If you receive it through an airdrop or reward → capital gain (general basis) at market value.
• If you buy it on the market → acquisition cost.
• When selling → GPO.

Fusion Mode: resolvers and gasless swaps

1inch has a mode called "Fusion" where swaps are executed by third parties ("resolvers") who take the price risk in exchange for MEV:

• The user does not pay gas (the resolver integrates it into the price).
• The resolver competes to execute the swap at the best time.
• Effective price may be slightly better with Fusion.

Fiscally: For the user, Fusion is the same as a normal swap. Value in/value out = result.

Other DEX aggregators: ParaSwap, CoW Protocol, UniswapX

CoW Protocol (Coincidence of Wants)

CoW Protocol matches orders from users who want opposite tokens (A wants ETH, B wants USDC) without going through AMMs. If there is no match, it goes to the DEX.

Fiscal: For the user, the same → transmission of the input asset, acquisition of the output asset.

UniswapX

UniswapX also has a model of fillers that compete to execute swaps. Includes gasless and cross-chain trading.

Fiscal: Same as a standard swap.

Gas: acquisition cost or expense

The gas fees paid in a swap operation are a higher acquisition cost of the asset received (or a lower transfer amount of the asset sold):

• In 1inch Fusion (gasless), gas is "included" in the price → it is already reflected in the exchange rate.
• In normal swap with gas → add the gas (in EUR) to the acquisition cost of the asset received.

Operations tracking in 1inch

1inch does not offer official history CSV. To declare:

1. Import your address into Koinly, Cointracking or Taxodio.
2. 1inch transactions appear as normal swaps (ETH → USDC).
3. Internal routing (if multi-hop: ETH → USDT → USDC in two internal steps) can generate multiple transactions in the explorer.

Attention to multi-hop: If an ETH → USDC swap passes internally through USDT (ETH → USDT → USDC), two transactions may appear in Etherscan. Fiscally they can be interpreted as two separate transmissions (ETH → USDT, then USDT → USDC). Some tracking tools consolidate it into a single event.

Summary table

Updated: April 2026 | Fiscal year: 2025