Polymarket Taxes UK
UK tax treatment of Polymarket activity involves two separate questions. The crypto funding leg - the USDC or other cryptoassets used to enter and exit positions - is subject to Capital Gains Tax analysis under Section 104 pooling rules, and this layer is well-defined under HMRC's cryptoasset guidance. The event-position profit or loss is a different matter entirely: HMRC has not published guidance specifically addressing prediction markets, and the correct classification is genuinely fact-sensitive. This guide works through both layers.
Preview your UK Polymarket tax report. Enter your proxy wallet, optionally add your History CSV, and DYOR.tax separates your crypto funding disposals from your event-position P/L for UK tax review.
Try the UK Polymarket Tax Calculator - free →How Polymarket Works for UK Tax Purposes
Polymarket is a decentralised prediction market platform on the Polygon blockchain. Users buy binary outcome contracts - "Yes" or "No" shares - settled in USDC. Winning shares redeem at $1 each on resolution; losing shares expire worthless. Positions can also be traded before settlement.
All trading runs through a proxy wallet - a smart contract address distinct from your sign-in wallet. Polymarket does not issue any tax documents equivalent to a UK broker statement, a self-assessment certificate, or any equivalent of the transaction summaries some centralised exchanges provide. Your transaction record lives on-chain.
For UK tax purposes, this matters because: (1) no third party will tell you what to declare - the obligation is entirely yours; and (2) HMRC may receive relevant transaction data from in-scope providers from 2027 onwards.
Layer 1 - Crypto Funding Disposals
The first layer is the simpler one. Every time you sell or convert a cryptoasset - including USDC - you trigger a chargeable disposal under HMRC's cryptoasset guidance. Section 104 pooling applies.
The typical funding chain for Polymarket users looks like this:
- Buy USDC with GBP: acquisition at your sterling cost, entering the USDC Section 104 pool
- Transfer USDC to your Polymarket proxy wallet: typically not a disposal where beneficial ownership remains with you - though this depends on the specific proxy structure
- Withdraw USDC from your proxy wallet: typically not a disposal on the same basis
- Sell USDC back to GBP: chargeable disposal - gain or loss = sterling proceeds minus Section 104 pool allowable cost
If you funded your account by swapping another cryptoasset into USDC - for example, ETH to USDC - that swap is itself a chargeable disposal of the ETH at its sterling market value at the time of the swap. Each step in the funding chain is assessed separately.
If USDC closely held its dollar peg and sterling was stable, the gain or loss on USDC may be very small. However, it is still calculable and reportable if your total CGT position exceeds the £3,000 Annual Exempt Amount or if your total disposal proceeds exceed £50,000 (for those already in Self Assessment). The gain does not disappear because the amount is small.
Layer 2 - Event-Position P/L (Review-Required)
The profit or loss on your Polymarket event positions is where the analysis becomes genuinely unsettled. Three distinct UK tax treatments are possible, and HMRC has not published guidance that addresses prediction markets directly.
Framework 1 - Gambling or exempt
If your Polymarket activity is characterised as a wagering contract, HMRC's betting manuals indicate that a punter's profits are ordinarily outside Income Tax and outside CGT. This is a longstanding principle in UK tax law: genuine gambling winnings by a punter are not taxable, and gambling losses are not relievable.
Having expertise, using systematic research, or even making a living from gambling does not, by itself, make the activity taxable as a trade under HMRC's betting guidance. The threshold for characterising someone as a professional gambling trader is high.
For some retail users, the gambling framework may be arguable, but this depends on the legal characterisation of the activity, which has not been confirmed by HMRC in any published guidance reviewed here.
Framework 2 - Capital gains
If the Polymarket position contracts are treated as capital assets - intangible property capable of being held and disposed of - then gains and losses would fall within Capital Gains Tax. The £3,000 Annual Exempt Amount would apply. Rates would be 18% (basic rate taxpayers) or 24% (higher or additional rate taxpayers) for 2025-26. Capital losses could be set against other capital gains.
Framework 3 - Trading income
If your activity is organised, systematic, and profit-seeking in a business-like way, HMRC could characterise it as a trade. Profits would then be taxable at your marginal Income Tax rate. Losses might be set against other income. HMRC applies a "badges of trade" test: relevant factors include frequency of transactions, degree of organisation, time devoted, use of specialist research, and whether the activity resembles a commercial business. This applies only in unusual cases and is far less common for ordinary retail participants.
Why This Matters for Your Self Assessment Return
The practical consequence of this ambiguity is that you cannot simply file a nil CGT return and assume the event-position P/L is tax-free without understanding how your specific activity would be characterised.
You also cannot ignore the crypto funding layer just because you think the event-position is gambling-exempt. The two layers are independent: your USDC disposals are subject to CGT analysis regardless of how the event-position outcome is classified.
For most retail users with modest activity, the practical steps are:
- Calculate your crypto funding disposals under Section 104 and determine whether they create a reportable CGT position
- Assess whether your event-position activity looks more like casual gambling, capital investment, or systematic trading - and seek advice if the amounts are material or your activity is high-volume
- Keep full records of both layers so you can demonstrate your position if HMRC asks
Gambling Commission Position - 4 February 2026
On 4 February 2026, the Gambling Commission published its position that current prediction-market products offered in Great Britain appear to fall within UK gambling law as betting-intermediary or betting-exchange style products, rather than as non-gambling products. The Commission also noted that operators not licensed to offer gambling services in Great Britain should not be targeting or transacting with consumers there.
This is a regulatory position under the Gambling Act 2005, not a tax ruling from HMRC. Gambling regulation and tax treatment are determined by different bodies under different legal frameworks. The Commission's position on regulatory classification may be relevant context when characterising the nature of your activity for tax purposes, but it does not determine your tax liability directly.
The regulatory position does add a separate compliance consideration for UK-based Polymarket users: use of the platform from Great Britain may raise questions under gambling law independent of any tax analysis.
Why Losses May Not Be Relievable
Under the gambling/exempt framework, losses are not relievable against other income or gains. This is the other side of the gambling exemption: the symmetry means that if profits are outside tax, losses provide no relief either.
Under the CGT framework, capital losses can be set against capital gains in the same year or carried forward. Under the trading income framework, trading losses may in some circumstances be set against other income.
If you have had significant Polymarket losses, the classification question becomes more important. Whether those losses are relievable depends entirely on which framework your activity falls within - and that cannot be determined without analysis of your specific facts.
CARF and Record-Keeping
The Cryptoasset Reporting Framework came into force in the United Kingdom on 1 January 2026. UK cryptoasset service providers are now required to collect customer tax-residence and transaction data. The first reporting window runs from 1 January 2027 to 31 May 2027, covering calendar year 2026.
Polymarket itself is a decentralised protocol and may not be directly within scope as a UK provider. However, centralised exchanges and wallet providers used to acquire USDC or other tokens may be in scope. HMRC may receive transaction data from in-scope providers from 2027 onwards. Keeping your own records is essential regardless of what third parties report.
For your Self Assessment return, retain:
- All on-chain transaction records from your Polymarket proxy wallet
- Exchange records for all USDC purchases and sales
- Records of any crypto-to-crypto swaps on the way to or from USDC
- Section 104 pool calculations for each cryptoasset used
- Your reasoning for how you characterised the event-position P/L
Common UK Polymarket Tax Mistakes
- Assuming all Polymarket activity is tax-free because gambling is exempt. The crypto funding leg is always a separate CGT analysis. The two layers must be assessed independently.
- Forgetting that swapping ETH to USDC is a chargeable disposal. Any crypto-to-crypto swap on the way to funding your Polymarket account is a UK taxable event, regardless of your Polymarket outcome.
- Not registering for Self Assessment. CGT on crypto funding disposals still requires a Self Assessment return if gains or proceeds exceed the relevant thresholds. Notify HMRC by 5 October 2026 for the 2025-26 tax year.
- Assuming high-frequency activity is gambling-exempt. High-volume, systematic, profit-seeking Polymarket trading may be reclassified as a trade by HMRC, removing any gambling exemption. The badges-of-trade test looks at frequency, organisation, and profit motive.
- Claiming gambling losses. Under the gambling framework, losses are not relievable. Claiming them against other income or gains when the activity may be treated as gambling would be incorrect.