Crypto arbitration: taxation in Spain
Crypto arbitrage consists of exploiting price differences of the same asset on different exchanges simultaneously. It's theoretically low risk: you buy where it's cheapest and sell where it's most expensive, capturing the difference. But fiscally, each operation is a taxable event.
Types of crypto arbitrage
1. Exchange Arbitrage (CEX-CEX):
- Bitcoin is trading at €30,000 on Kraken and €30,050 on Coinbase.
- You buy on Kraken, sell on Coinbase instantly.
- Earning: €50 per BTC (less commissions).
2. DEX-CEX Arbitrage:
- ETH is €2,000 on Uniswap and €2,020 on Binance.
- You buy on Uniswap (including gas) and sell on Binance.
3. Triangular:
- BTC/ETH → ETH/BNB → BNB/BTC → if the sequence closes with a profit.
4. Cross-chain:
- Same asset, different chains. Requires bridges.
Each operation is a tax event
Arbitrage generates dozens, hundreds or thousands of trades per day. Every purchase and sale is a tax event. If you use automated bots, you can have millions of events in a year.
The administrative burden is astronomical if you don't have the right tools.
Economic activity or capital gains?
If the arbitration is:
- Sporadic and unstructured: Capital gains, basis of savings.
- Regular, organized, with bots: Economic activity, general basis, personal income tax scale up to 47%.
The line is interpretive, but if you have bots running 24/7, capital dedicated exclusively to this and you see income as a regular main/complementary source, it is most likely economic activity.
The commission trap
Arbitrage seems profitable but commissions can eliminate margin:
- Trading commissions (0.1% each side → 0.2% per operation).
- Gas (Ethereum): may be more than the arbitrage margin.
- Order book spread.
- Slippage running.
Fiscally: Commissions are deductible from the result. A transaction with a net loss (due to commissions) generates a tax loss.
Pegged stablecoin arbitrage
Some stablecoins temporarily “unstick.” For example, USDC at €0.985 on an exchange.
- USDC purchases at €0.985.
- You sell USDC at €1 when the parity recovers.
- Profit: €0.015 per USDC → 1.5%.
This is perfectly valid fiscally. The gain is a capital gain based on savings.
Arbitration risks and their fiscal impact
Execution risk: The price changes while you execute → the trade may close with a loss.
Liquidity risk: You cannot close the other leg of the operation → you lose.
Counterparty Risk: Exchange goes down or has problems.
Losses are deductible, just as gains are taxable.
Arbitration bots: who is the taxpayer?
If you use an automated bot (Hummingbot, running on your server):
- You are the passive subject. The bot is just a tool.
- The bot's profits/losses are yours.
- If the bot operates through a company → the company pays taxes (IS).
If you use a third-party bot ("copy trading" or bot platform):
- It's still your profit/loss.
- But the one on the platform can retain or not.
How to manage the registration of thousands of operations
For high frequency arbitration, it is essential:
- Export all exchange trades (CSV).
- Use specific software: Koinly, Blockpit, CryptoTax (multi-exchange support).
- Verify that the software calculates FIFO correctly between exchanges.
- Consider hiring a tax advisor specialized in high frequency trading.
Updated: April 2026 | Fiscal year: 2025