Stablecoins Explained: How USDT, USDC and UK Alternatives Work

Stablecoins are the most important infrastructure in the crypto world that most people have never thought about. They are the bridge between traditional money and the blockchain economy — digital tokens designed to hold a steady value, usually pegged to the US dollar. Without stablecoins, most of crypto trading and decentralised finance simply could not function at the scale it does today.

But stablecoins are not all the same. Some are backed by real assets held in regulated banks. Some are backed by other cryptocurrencies. Some were backed by nothing except an algorithm — and several of those have collapsed catastrophically, wiping out billions in investor funds. Understanding how stablecoins work, which ones are used in the UK, and what the FCA thinks of them is essential knowledge for any serious crypto investor.

What Is a Stablecoin?

A stablecoin is a cryptocurrency designed to maintain a stable value relative to a reference asset — usually the US dollar, though some are pegged to the euro, the British pound or a basket of currencies. While Bitcoin and Ethereum fluctuate by 5-10% in a single day, USDT and USDC consistently trade within fractions of a penny of $1.00.

The stable value is what makes them useful. Stablecoins can be moved across borders in minutes with fees of a few pence. They can earn yield in DeFi protocols without the price volatility of holding ETH or BTC. They allow anyone, anywhere in the world, to hold dollar-denominated assets without needing a US bank account.

As of mid-2026, the global stablecoin market cap stands at approximately £140 billion, with USDT and USDC together accounting for over 85% of that total. Stablecoins settle trillions of pounds in transactions every year — more than some major traditional payment networks process monthly.

The Main Types of Stablecoins

Fiat-backed stablecoins are the most straightforward. The issuer holds real cash and cash equivalents in reserve — at least in theory — and issues tokens on a one-for-one basis. Every USDC token is supposed to be backed by one US dollar in a bank account or short-term treasury bill. USDT and USDC are the dominant examples of this category, together holding over £125 billion in assets as of 2026.

Crypto-backed stablecoins maintain their peg by holding other cryptocurrencies as collateral — usually significantly more collateral than the stablecoins issued, to absorb price volatility. MakerDAO’s DAI is the leading example. You deposit ETH as collateral and receive DAI, which remains pegged to $1 through over-collateralisation and automated liquidation mechanisms that kick in if collateral values fall too sharply.

Algorithmic stablecoins attempt to maintain a peg through supply-and-demand mechanisms rather than reserves. When the price rises above $1, more tokens are minted to bring it down. When it falls below $1, tokens are burned. TerraUSD (UST) was the most prominent algorithmic stablecoin — until May 2022, when it lost its peg and collapsed to nearly zero within 72 hours, wiping out approximately £40 billion in value and triggering a global crypto bear market.

How USDT (Tether) Works

Tether (USDT) is the oldest and largest stablecoin, launched in 2014. As of mid-2026, its market cap is approximately £110 billion, making it the third-largest cryptocurrency by value after Bitcoin and Ethereum. It is issued by Tether Limited, a company registered in the British Virgin Islands and operating out of Hong Kong.

Tether claims that every USDT is backed by real assets — initially dollars in a bank, but now a mix of US Treasury bills, money market funds, secured loans and other assets. Tether publishes quarterly attestations of its reserves, though these are not full independent audits in the traditional accounting sense.

Tether’s opacity has been a persistent source of controversy. In 2021, Tether and its sister company Bitfinex paid $41 million to settle US Commodity Futures Trading Commission charges related to misrepresentations about its reserve backing. Despite this, USDT remains the dominant stablecoin for crypto trading globally, particularly in Asia and emerging markets.

For UK users, USDT is available on most major exchanges. The FCA does not regulate Tether Limited as a UK entity, so USDT does not benefit from UK consumer protections. If Tether were to fail, UK holders would have limited legal recourse through UK courts.

How USDC (Circle) Works

USD Coin (USDC) was launched in 2018 by Circle, a Boston-based fintech company, in partnership with Coinbase. It has grown to approximately £30 billion in market cap as of mid-2026 and is widely regarded as the more transparent and regulated of the two major stablecoins.

Circle publishes monthly reserve reports audited by Deloitte, one of the Big Four accounting firms. USDC reserves are held in cash and short-duration US Treasury bills at regulated US financial institutions. Circle is licensed as a money transmitter in 45 US states and holds an Electronic Money Institution licence in Europe, giving it a regulatory footprint that Tether lacks.

USDC suffered a brief but significant crisis in March 2023, when Circle disclosed that £3.3 billion of its reserves were held at Silicon Valley Bank, which was collapsing at the time. USDC briefly fell to £0.87 before recovering when the US government intervened to guarantee SVB deposits. The episode highlighted that even a well-regulated stablecoin is not completely risk-free — counterparty risk to the banking system is real.

UK Stablecoin Regulation: The FCA’s Approach

The UK has been one of the most proactive major economies in developing a stablecoin regulatory framework. The Financial Services and Markets Act 2023 gave the FCA and Bank of England new powers to regulate stablecoins used for payment in the UK — a significant development that brought stablecoins within the scope of formal financial regulation for the first time.

Under the proposed framework, stablecoins used as a means of payment in the UK will need to be issued by FCA-authorised entities. The issuer must maintain full reserve backing for all tokens in issue, segregate reserves from company assets, publish regular audited reserve reports and meet minimum capital requirements. Foreign stablecoins like USDT may need to be issued by UK-registered entities or otherwise conform to UK rules to be marketed to UK retail consumers.

The Bank of England is separately exploring a digital pound — a central bank digital currency (CBDC) that would be a government-issued stablecoin backed by the full faith of the UK government. Consultation on the digital pound has been ongoing since 2023. Any rollout is expected no earlier than 2028, and the Bank has repeatedly emphasised it has not yet made a final decision on whether to proceed.

The Risks of Holding Stablecoins

The TerraUSD collapse in May 2022 demonstrated the most catastrophic stablecoin risk: de-pegging. A stablecoin that loses its peg to the dollar is no longer stable — it can collapse to near zero, as UST did, taking investors’ savings with it in a matter of hours. UK investors who held UST lost the full value of their positions with no recourse.

Even well-backed stablecoins carry counterparty risk. If the issuer becomes insolvent, or if the reserves are not as reported, holders could lose money. The USDC/SVB incident of 2023 showed how quickly a confidence crisis can develop, even for a transparently run stablecoin. Recovery was swift in that case — but it may not always be.

Regulatory risk is growing. If UK regulators require all stablecoin issuers to obtain FCA authorisation — and if major issuers like Tether cannot or will not comply — access to those stablecoins could be restricted for UK residents, creating operational disruption for those who hold or trade them.

Smart contract risk applies when stablecoins are used in DeFi. USDC and USDT held directly in a self-custody wallet are not exposed to smart contract risk. But the same coins deposited into a DeFi lending protocol are exposed to any bugs or exploits in that protocol’s code — a risk that exists independently of the stablecoin issuer’s solvency.

How to Use Stablecoins Safely in the UK

For UK investors who want to hold stablecoins, USDC is generally regarded as the safer option due to its monthly audited reserves, regulated issuer, strong institutional relationships and greater overall transparency. USDT offers greater liquidity on exchanges and is more widely accepted in peer-to-peer crypto markets, but its reserve history and regulatory posture are weaker.

Hold stablecoins only on regulated, FCA-registered exchanges or in self-custody wallets. Avoid holding large amounts on unregulated platforms. If you hold stablecoins on an exchange and the exchange becomes insolvent — as happened with FTX in November 2022 — you may lose access to your funds and have very limited legal recourse.

Understand the yield risks. Some platforms offer unusually high interest rates on stablecoin deposits — 10%, 15%, even higher. These yields are not risk-free. They typically come from lending your stablecoins to risky borrowers, providing liquidity in volatile DeFi markets, or from unsustainable tokenomics. If it looks too good to be true, it usually is. Celsius, BlockFi and Voyager all offered high stablecoin yields before collapsing in 2022.

The UK Tax Position on Stablecoins

HMRC’s guidance makes clear that stablecoins are cryptoassets subject to UK tax law. Converting pounds sterling to USDC is generally not a taxable event — you are buying an asset, not disposing of one. But converting USDC to another cryptocurrency is a disposal for capital gains tax purposes, even if your USDC has been worth exactly $1 throughout.

Earning yield on stablecoins may be treated as income, subject to Income Tax and National Insurance. HMRC considers DeFi stablecoin lending income on a case-by-case basis but has indicated it will generally treat returns on lending as income rather than capital gains.

HMRC updated its cryptoasset guidance in 2024 to specifically address DeFi stablecoin activity. UK investors who hold significant stablecoin positions should keep detailed records of all transactions — including DeFi swaps, yield receipts and platform transfers — and report accurately on their Self Assessment tax return.

What This Means for UK Investors

Stablecoins have become fundamental infrastructure for the crypto economy. They underpin crypto trading, DeFi, cross-border payments and an increasing number of traditional financial products. UK investors who engage with crypto in any serious way will encounter stablecoins constantly.

The FCA’s regulatory framework, when fully implemented, should provide greater clarity and consumer protection for UK residents holding regulated stablecoins. It should create a clearer distinction between FCA-authorised stablecoins that can be marketed to UK retail consumers and unregulated ones that cannot.

For now, stablecoins sit in a regulatory grey zone. They are not covered by the FSCS. They are not regulated investments. They are not banking deposits. They are a new category of digital asset with genuinely new risks — and UK investors should approach them with that in mind, treating them as useful infrastructure rather than guaranteed safe havens.

This article is for educational purposes only and does not constitute financial advice. Cryptocurrency investments involve significant risk. Always do your own research.