Prediction market tax
in the UK
The UK has a uniquely favourable framework for recreational gamblers: gambling winnings are not taxable income. But whether prediction markets count as gambling under HMRC's view is unsettled. USDC itself is a cryptocurrency and triggers its own capital gains obligations when disposed of. This guide explains both scenarios and what they mean for your tax position.
Gambling income vs CGT, which applies?
If HMRC treats prediction market activity as gambling by a recreational individual, winnings are not assessable income under UK law. The UK has not taxed gambling winnings since the 19th century. No Self Assessment reporting required for the gambling gains themselves.
If USDC is treated as a capital asset (per HMRC crypto guidance), each disposal is a CGT event. Rate: 10% (basic rate taxpayer) or 20% (higher/additional). Annual exempt amount: £3,000 (2024-25).
Capital gains tax in practice
How HMRC treats USDC
HMRC treats all cryptoassets, including stablecoins like USDC: as capital assets, not currency (HMRC guidance CRYPTO10150). Each disposal triggers a capital gains event. Cost basis is set in GBP at the time of acquisition via the Section 104 pool average cost method.
Because USDC pegs to USD, your cost basis and proceeds are measured in GBP at the exchange rate on each date. Even if USDC holds its USD value perfectly, GBP/USD movement creates a CGT gain or loss. A 10% GBP depreciation creates a 10% CGT gain even if nothing changed in USD terms.
Crypto gains above the £3,000 annual exempt amount must be reported on your Self Assessment tax return (SA100 + supplementary pages). HMRC has a specific crypto section in Self Assessment. Trading tools like Koinly (koinly.io) and CoinTracking support HMRC-format reports for Polygon USDC transactions.
Unlike shares, crypto uses a single pool per token type. All USDC purchases are pooled at an average cost. When you dispose of USDC (converting to GBP or other assets), the gain is calculated against the pool average. Keep records of every USDC purchase date, GBP value, and disposal.