Summary: The taxability of Polymarket winnings in the UK hinges on HMRC's classification of your trading behaviour. Those engaging in occasional prediction market activity may benefit from the gambling exemption (no tax liability). Regular or professional traders will likely be subject to either Income Tax or Capital Gains Tax. HMRC continues to develop its stance on crypto-based prediction platforms — maintain comprehensive records of all transactions.
Determining the correct tax treatment for Polymarket winnings remains a pressing concern for UK-based prediction market participants. This article examines the current HMRC position on Polymarket tax UK in 2026, drawing on official HMRC guidance regarding cryptoassets and gambling-related income.
⚠️ Not tax advice. Your individual tax position depends on your specific circumstances. Seek guidance from a qualified UK tax professional or chartered accountant before making any declarations.
Three Possible Tax Treatments
HMRC has not released dedicated guidance on prediction market contracts. Drawing on current HMRC rules governing cryptoassets and gambling activities, three distinct tax treatments are possible:
Treatment 1: Gambling Winnings (Tax-Free)
Should HMRC classify your Polymarket participation as gambling, your winnings would be exempt from UK taxation under established gambling exemptions. This represents the most advantageous outcome and may apply where:
- Your market participation is sporadic rather than methodical
- You do not rely on this activity as your primary or secondary income
- Your behaviour aligns with consumer gambling rather than professional investment
Established UKGC-regulated betting platforms (Betfair, Smarkets) unambiguously qualify as tax-exempt gambling. Polymarket operates on blockchain infrastructure and falls outside the Gambling Act's scope — HMRC may decline to extend the same exemption without explicit confirmation.
Treatment 2: Capital Gains Tax (CGT)
HMRC's Cryptoassets Manual treats most cryptoasset transactions as capital events liable to CGT. Under this framework:
- Each profitable position represents a USDC disposal triggering a gain
- CGT rates: 18% (standard rate) or 24% (higher/additional rate) from April 2024 onwards
- Annual exemption: £3,000 (2026/27 tax year) — gains within this threshold incur no tax
- Capital losses offset capital gains in the same or subsequent years
- USDC settlement proceeds count as disposal consideration
Under CGT treatment, modest traders whose annual gains remain below £3,000 face no tax burden. Higher-volume traders must report on Self Assessment within the Cryptoassets section.
Treatment 3: Income Tax (Trading Income)
Should HMRC determine your Polymarket engagement constitutes a trade, your winnings become taxable income subject to Income Tax:
- Tax rates: 20% (basic), 40% (higher), 45% (additional)
- Self-employment National Insurance contributions may be due
- Trading losses can be carried forward to offset future trading profits
- Likely to apply where: activity is regular and organised, demands substantial time commitment, forms a primary or secondary income stream
HMRC's Published Guidance on Cryptoassets
HMRC released its Cryptoassets Manual (CRYPTO) in 2022, with revisions published in 2024. The following points bear directly on Polymarket transactions:
- USDC, as a stablecoin, qualifies as a cryptoasset — each disposal triggers CGT
- Exchanging crypto to acquire prediction market tokens may constitute a taxable disposal event (USDC conversion)
- HMRC has issued no dedicated classification for prediction market contracts
- New cryptoasset reporting obligations effective 2025 require UK-regulated platforms to furnish HMRC with transaction data — HMRC is systematically gathering intelligence on user activity
Practical Record-Keeping for UK Polymarket Traders
Whichever tax treatment ultimately applies, preserve the following documentation:
- Deposit records: date, sterling amount transferred, USDC received, applicable exchange rate
- Market activity: position opening date, USDC amount wagered, resolution date, USDC settlement amount
- Withdrawal records: date, USDC quantity withdrawn, sterling equivalent received, exchange platform used
- Year-end reconciliation: cumulative USDC inflows, cumulative USDC outflows, net gain or loss expressed in sterling
Platforms such as Koinly and CoinTracker facilitate Polymarket/Polygon transaction tracking and produce HMRC-aligned CGT computations automatically.
The Gambling Tax-Free Argument in Practice
Certain UK Polymarket participants contend their returns constitute gambling winnings and thus remain untaxed, citing parallels with Betfair Exchange (which clearly qualifies as tax-exempt). This argument carries some logical force for casual participants yet encounters two material challenges:
- Polymarket operates without UKGC licensing — HMRC has not confirmed whether the gambling exemption applies to unregulated overseas platforms
- The blockchain-based structure means HMRC perceives transactions as cryptoasset disposals rather than gambling activity
In the absence of definitive HMRC guidance, the prudent course involves reporting under CGT principles whilst noting the gambling exemption as an alternative legal position.
Reporting Polymarket Winnings on Self Assessment
Where reporting becomes necessary (gains exceeding £3,000 or income surpassing £1,000):
- File Self Assessment SA100 (via HMRC's online Personal Tax Account where available)
- For CGT scenarios: complete SA108 — enter cryptoasset disposals under "Other property, assets and gains"
- For trading income scenarios: complete SA103 (self-employed) or SA800 (partnership structures)
- Submission deadline: 31 January following the relevant tax year
FAQ — Polymarket Tax UK
- Do I need to tell HMRC about small Polymarket winnings?
- Provided your aggregate capital gains from all sources (including USDC transactions) fall beneath £3,000 in 2026/27, no reporting obligation arises. Where you are a basic rate taxpayer with gains under £3,000, no tax liability materialises and no disclosure is necessary.
- Are losses on Polymarket tax-deductible?
- Under CGT treatment, yes — capital losses can be set against capital gains within the same year or carried forward. Under trading income treatment, losses similarly offset other trading profits. Maintain detailed records of all unsuccessful positions.
- Does HMRC know about my Polymarket activity?
- From 2025 onwards, cryptoasset regulatory requirements oblige UK-regulated exchanges (Coinbase UK, Kraken) to furnish HMRC with user transaction data exceeding £1,000 annually. Transactions identifiable as prediction market engagement may prompt HMRC investigation where not previously declared.