Crypto glossary
Forms 172 and 173 (Spain)
Forms 172 and 173 are Spanish informative returns in which crypto service providers report their customers' balances and transactions to the tax agency.
Spain introduced both returns under its 2021 anti-fraud law, and providers file them each January for the previous year. Modelo 172 covers balances: entities resident in Spain, or operating there through a permanent establishment, that safeguard private keys or hold virtual currencies on behalf of customers report each customer's holdings at 31 December, with their market value. Modelo 173 covers operations: providers of exchange, transfer and similar services report acquisitions, sales, swaps, transfers and payments made by their customers during the year, and issuers in initial offerings report their sales.
Together with Modelo 721, which taxpayers file for crypto held abroad, these returns give the Spanish tax agency (AEAT) a broad view of residents' crypto activity. The data feeds the agency's checks on income tax and wealth tax returns, and mismatches can trigger letters or audits.
From 2026 the EU DAC8 directive adds a harmonised reporting regime for crypto-asset service providers across member states, so the Spanish domestic returns are being aligned with, and partly replaced by, the European framework.
Example
A Spanish user forgets to declare a crypto sale. Months later the tax agency sends a letter, because the exchange's Modelo 173 reported the transaction under her tax ID.