Wash trading and manipulation in crypto: tax and legal risks

The crypto market has historically had high levels of manipulative activity. Wash trading, pump & dump and other practices are illegal and have serious tax consequences. This is what you need to know.

What is wash trading?

Wash trading consists of buying and selling the same asset repeatedly between own or coordinated accounts to:

1. Generate artificial trading volume (to position an exchange or token in rankings).
2. Create fictitious losses to reduce the tax bill (tax wash sale).
3. Inflate the apparent liquidity of an asset.

In Spain: Wash trading is prohibited by the European Market Abuse Regulation (MAR) and, although crypto assets were outside the historical scope of MAR, MiCA 2024 explicitly includes them.

Tax loss harvesting and "wash sale"

In the United States there is a "wash sale" rule that specifically prohibits selling an asset at a loss and repurchasing it in less than 30 days to take advantage of the deduction. In Spain there is no explicit rule for cryptocurrencies.

What does this entail?

• You can sell BTC at a loss, buy back BTC immediately and declare the loss.
• It is a legal practice of tax loss harvesting in Spain (as long as they are real operations).
• The main difference: if you sell and repurchase between related parties (own accounts of the same person), it can be considered a linked transaction without market value.

Operations between own wallets with fictitious profit

A case closer to tax fraud: creating fictitious profits.

• I transfer 1 BTC from wallet A to wallet B and "note" that I sold it high.
• In reality there is no real transmission → the "income" is fictitious.

Risk: If you try to justify false income or inflate tax bases (for example, to obtain bank loans), this represents tax fraud or document falsification.

Pump & Dump: whoever sells on time wins, legally

The Pump & Dump scheme works like this:

1. Silent accumulation of a weak token.
2. Aggressive promotion on social networks to attract buyers.
3. Sale when the price rises → real profit for the organizers.
4. The last buyers lose when the price collapses.

Fiscally for the organizer: The profits from the pump & dump are real capital gains and are subject to personal income tax. The activity itself may constitute a crime of market manipulation (art. 284 Penal Code).

Fiscally for victims: Losses are deductible as property losses.

How the Treasury detects suspicious activities

The AEAT uses:

1. Exchange data crossing: Exchanges report to the AEAT using Form 172. Huge volumes are warning signs.
2. On-chain analysis: Collaboration with blockchain analytics companies (Chainalysis, Crystal).
3. Unusual trading patterns: Many small trades in a short time may indicate suspicious automated activity.
4. Comparison between trading volume and declared income: If your monthly volume is €10M but you declare €30,000 of income → alert.

Consequences of tax fraud with crypto

If the Treasury determines that there was tax fraud:

• Slight penalty: 50% of the amount defrauded.
• Serious penalty: 100-150% if there is concealment.
• Tax crime: If the fraud exceeds €120,000 in a year → prison sentence of 1 to 5 years.
• Crime of money laundering: If undeclared crypto profits are integrated into the assets.

Tip: transparency is always the best strategy

Although the crypto market is volatile and unpredictable, taxation is always easier with clear records:

• Declare all your winnings, even the small ones.
• Do not try to create fictitious losses: it does not work and the risk is disproportionate.
• On-chain anonymity does not protect if the money eventually reaches your bank account.

Updated: April 2026 | Fiscal year: 2025