In this guide
Summary: The tax position on Polymarket winnings in the UK hinges on HMRC's classification of your trading behaviour. Those who trade occasionally may benefit from the gambling exemption (no tax liability). Active or professional traders will likely face either Income Tax or Capital Gains Tax obligations. HMRC guidance on crypto-based prediction markets continues to evolve — maintain comprehensive records of all activity.
Polymarket tax treatment remains a pressing concern for UK-based prediction market participants. This guide examines the current HMRC stance on Polymarket taxation in the UK throughout 2026, drawing on official HMRC guidance regarding cryptoassets and gambling-related income.
⚠️ Not tax advice. Your specific tax position depends on your individual circumstances. Seek guidance from a qualified UK tax professional or chartered accountant for bespoke advice tailored to your situation.
Three Possible Tax Treatments
HMRC has not released tailored guidance specifically addressing prediction market contracts. Based on current HMRC frameworks governing cryptoassets and gambling activities, three distinct tax treatments are possible:
Treatment 1: Gambling Winnings (Tax-Free)
Should HMRC classify your Polymarket activity as gambling, your winnings would be fully exempt from UK taxation under existing gambling exemption rules. This represents the most advantageous scenario and may apply when:
- Your trading occurs infrequently and lacks systematic patterns
- You do not regard it as a main or auxiliary income stream
- Your conduct aligns with consumer gambling behaviour rather than investment strategy
Conventional UKGC-regulated betting platforms (Betfair, Smarkets) unambiguously qualify as tax-exempt gambling. Polymarket operates on blockchain technology and falls outside the Gambling Act framework — HMRC may decline to extend the same exemption without explicit confirmation.
Treatment 2: Capital Gains Tax (CGT)
HMRC's Cryptoassets Manual treats most cryptoasset sales as chargeable gains subject to CGT. Under this framework:
- Each profitable trade represents a USDC disposal triggering a gain
- CGT rates: 18% (standard rate) or 24% (higher/additional rate) effective from April 2024
- Annual allowance: £3,000 (2026/27) — gains below this threshold incur no tax
- Offsetting losses against gains is permitted
- USDC received upon settlement constitutes disposal proceeds
Where CGT applies, modest traders generating gains beneath £3,000 annually face zero tax liability. Larger-scale traders must declare on Self Assessment under the Cryptoassets section.
Treatment 3: Income Tax (Trading Income)
Should HMRC determine your Polymarket participation constitutes a trade, your winnings become taxable income subject to Income Tax:
- Tax rates: 20% (standard), 40% (higher), 45% (additional)
- Self-employment National Insurance contributions may be applicable
- Trading losses can be carried forward to offset subsequent trading income
- Probable application if: activity is regular, occupies considerable time, forms a primary or secondary income source
HMRC's Published Guidance on Cryptoassets
HMRC released its Cryptoassets Manual (CRYPTO) in 2022, with further updates in 2024. Relevant considerations for Polymarket traders include:
- USDC, being a stablecoin, constitutes a cryptoasset — CGT applies upon disposal
- Exchanging crypto to acquire tokens or contracts may trigger a taxable event (USDC disposal)
- HMRC has not yet established a dedicated framework for prediction market contracts
- From 2025 onwards, UK-regulated exchanges face mandatory reporting obligations — HMRC is accumulating transaction data to build enforcement intelligence
Practical Record-Keeping for UK Polymarket Traders
Irrespective of the ultimate tax classification, preserve the following documentation:
- Each deposit transaction: date, GBP value, USDC quantity received, applicable exchange rate
- All market positions: opening date, USDC committed, resolution date, USDC returned
- Every withdrawal: date, USDC withdrawn, GBP equivalent, exchange platform used
- Year-end reconciliation: cumulative USDC inflows, cumulative USDC outflows, net GBP profit or loss
Platforms such as Koinly and CoinTracker facilitate importing Polymarket and Polygon transactions, automatically generating tax-compliant CGT computations for HMRC submission.
The Gambling Tax-Free Argument in Practice
Certain UK Polymarket participants contend their winnings qualify as gambling proceeds and therefore remain untaxed, citing parallels with Betfair Exchange (demonstrably tax-exempt). Whilst this argument carries logical weight for casual traders, it encounters two significant hurdles:
- Polymarket lacks UKGC licensing — HMRC has not confirmed whether the gambling exemption extends to unlicensed international platforms
- The blockchain-based transaction structure leads HMRC to categorise these as cryptoasset disposals rather than gambling outcomes
Absent definitive HMRC pronouncement, the prudent strategy involves reporting under CGT whilst documenting the gambling-exemption reasoning as a secondary interpretation of your position.
Reporting Polymarket Winnings on Self Assessment
Where reporting obligations arise (gains exceeding £3,000 or income surpassing £1,000):
- Complete Self Assessment SA100 (or file electronically via HMRC's Personal Tax Account portal)
- For CGT: complete SA108 — record cryptoasset disposals within the "Other property, assets and gains" category
- For trading income: complete SA103 (self-employment) or SA800 (partnerships)
- File by 31 January following the tax year conclusion
FAQ — Polymarket Tax UK
- Do I need to tell HMRC about small Polymarket winnings?
- Provided your aggregate capital gains from all sources (encompassing USDC transactions) remain below £3,000 during 2026/27, reporting is unnecessary. For basic rate taxpayers with gains beneath £3,000, no tax liability arises and notification to HMRC is not required.
- Are losses on Polymarket tax-deductible?
- Under CGT treatment, yes — losses can be matched against capital gains within the same or subsequent tax years. Under trading income treatment, losses similarly offset other trading income. Retain documentation of all unprofitable positions.
- Does HMRC know about my Polymarket activity?
- The 2025 cryptoasset reporting regime requires UK-regulated exchanges (Coinbase UK, Kraken) to disclose user transactions exceeding £1,000 annually to HMRC. Transactions identifiable as prediction market activity may prompt HMRC investigations targeting non-compliant traders.