USDT and stablecoins: how are they taxed in Spain?
The popular perception is that stablecoins "have no risk" and therefore do not generate tax obligations. This is partially true, but there are situations where stablecoins do produce taxable events.
What are stablecoins?
They are cryptocurrencies designed to maintain a stable value against a reference currency, usually the dollar (USDT, USDC, BUSD…) or the euro (EURS, EURT…). They can be backed by:
- Fiat reserves: USDT, USDC.
- Cryptocurrencies: DAI (overcollateralized in ETH).
- Algorithms: so-called "algorithmic stablecoins" (many have collapsed, such as Terra's UST).
When are stablecoins taxed?
When exchanging another crypto for a stablecoin
If you sell BTC and receive USDT in exchange, a taxable event is generated — it is a transfer of BTC. The gain is calculated by comparing the value in euros of the USDT received against the FIFO cost of the BTC delivered.
When exchanging a stablecoin for another crypto
Buying ETH with USDT is a transfer of USDT. Under normal circumstances, given that USDT is always worth ≈ 1 USD, the difference between the acquisition cost and the transfer value of the USDT is minimal or zero. However, there may be a small gain/loss if the EUR/USD exchange rate fluctuated.
Stablecoins that lose their peg
If USDT or USDC is temporarily worth 0.97 USD and you sell at that moment, you may have a small tax loss. In the extreme case of a total collapse (like Terra's UST), the loss may be total.
Interest on stablecoins
Lending your USDT in DeFi protocols or on centralized platforms generates income from movable capital (rendimientos del capital mobiliario), reportable in the year of accrual.
Stablecoins and the EUR/USD exchange rate
This point confuses many users. When you buy USDT with euros at €0.92/USDT and then use it when it is at €0.95/USDT:
- You have obtained a small capital gain of €0.03 for each USDT.
- It must be declared, even if it is small.
In practice, many tools omit these minimal differences or round them off, but technically the obligation exists.
The Terra/LUNA collapse and taxation of the loss
If you held Luna's UST and lost all your capital, you can declare that loss as a capital loss (pérdida patrimonial) in the fiscal year in which the collapse occurred (May 2022), provided you have documented that the tokens definitively lost their value.
This loss offsets gains from other assets in that fiscal year or in the following 4 years.
Stablecoins in Forms 172 and 173
Stablecoins are subject to the same information forms as other cryptocurrencies. If you hold more than €1,000 in USDT as of December 31, you must include them in Modelo 172.
Conclusion
Stablecoins are not tax-exempt. Every exchange can generate a minor taxable event, interest is reportable income, and losses from collapses can be deductible. The treatment is identical to that of any other cryptocurrency.