In this guide
Key difference: Spread betting profits are tax-free under UK law. Prediction market winnings (from crypto-based platforms like Polymarket) may be subject to CGT or Income Tax. For UKGC-regulated, tax-free event betting, Betfair Exchange is the closer comparison. For market breadth and lowest fees, Polymarket via PolyGram wins.
UK-based traders can access two primary mechanisms for generating returns through accurate outcome forecasting: spread betting (via FCA-licensed financial spread betting operators) and prediction markets (via Polymarket, Betfair Exchange, or Smarkets). Grasping these distinctions matters significantly for structuring your tax position and selecting appropriate trading instruments.
What Is Spread Betting in the UK?
The UK's FCA-regulated spread betting sector includes operators such as IG, CMC Markets, and Spreadex. Participants stake a sum per point shift in a financial asset (FTSE 100, currency pairs, individual equities). Core features include:
- Leverage: Ranges from 2:1 to 20:1 based on the underlying asset category
- Tax-free profits: Under UK law, spread betting is legally treated as gambling — winnings carry no tax liability, and losses cannot be offset
- FCA regulated: Comprehensive investor safeguards, mandatory negative balance protection included
- Markets: Financial instruments only (stock indices, currency markets, raw materials, equities) — excludes political or sporting events
- Bid-ask spread: Embedded transaction cost (normally 1–3 pips on major currency pairs)
What Are Prediction Markets?
These platforms enable you to acquire YES/NO binary contracts tied to actual real-world occurrences. Primary UK-available platforms:
- Polymarket (via PolyGram): 8,400+ markets, USDC settlement, ~1% effective cost, regulatory status unclear
- Betfair Exchange: 500 markets, Sterling settlement, 5% commission, UKGC authorised
- Smarkets: 200 markets, Sterling settlement, 2% commission, UKGC authorised
Tax Treatment — The Critical Difference
Spread Betting: Tax-Free
Across the board, spread betting returns are free from Capital Gains Tax and Income Tax in the UK, provided your account is held with an FCA-authorised operator. This represents one of the most valuable tax advantages accessible to UK retail investors. HMRC's official guidance confirms this treatment for financial spread betting activity.
Betfair Exchange / Smarkets: Tax-Free
Winnings from UKGC-regulated betting exchanges receive identical tax treatment — classified as gambling income under the Gambling Act 2005. Consequently, Betfair and Smarkets deliver the optimal combination: prediction market functionality alongside unambiguous tax-free classification.
Polymarket: Tax Uncertain
Polymarket returns do not fit neatly within either the gambling exemption (lacks UKGC authorisation) or the spread betting exemption (not an FCA-authorised financial spread betting provider). HMRC could potentially classify these as CGT or Income Tax liabilities. See our UK tax guide.
Comparison — Spread Betting vs Prediction Markets
| Factor | Spread Betting | Betfair/Smarkets | Polymarket (PolyGram) |
|---|---|---|---|
| UK Tax Status | Tax-free ✅ | Tax-free ✅ | Uncertain ⚠️ |
| Regulation | FCA ✅ | UKGC ✅ | Grey zone |
| Leverage | Up to 20:1 | None | None |
| Markets | Financial only | ~200–500 | 8,400+ |
| Max Profit | Unlimited (leveraged) | 2x (binary) | Up to 100x (low-prob YES) |
| Max Loss | Unlimited (leveraged) | Stake only | Stake only |
| GBP Deposits | Yes ✅ | Yes ✅ | Via crypto |
| Effective Costs | 1–3% spread | 2–5% | ~1% |
When to Use Spread Betting vs Prediction Markets
Choose Spread Betting When:
- You seek leveraged positions in financial instruments (FTSE 100, currency pairs)
- Certainty regarding tax-free treatment is essential and you require regulatory clarity
- Your trading focuses on financial price fluctuations rather than discrete event outcomes
- You require FCA negative balance safeguards
Choose Prediction Markets When:
- You possess demonstrable skill in anticipating particular real-world events (political contests, athletic competitions, scientific developments)
- You prefer a bounded-loss, binary framework (maximum loss equals your stake)
- You require access to markets unavailable through spread betting operators (political contests, blockchain events, meteorological outcomes)
- Minimising fees relative to conventional betting operations is a primary concern
Best Combined Approach for UK Traders:
- Deploy an FCA-regulated spread betting account (IG, CMC) for financial instrument positions where leverage and tax-free status are strategically important
- Deploy Smarkets or Betfair Exchange for UK-focused politics and athletics — UKGC-authorised, tax-free treatment, Sterling-denominated
- Deploy Polymarket via PolyGram for markets with no equivalent elsewhere (8,000+ international event contracts) — while acknowledging tax ambiguity or maintaining detailed records
FAQ — Spread Betting vs Prediction Markets UK
- Is Betfair Exchange classed as spread betting?
- No — Betfair Exchange operates as a betting exchange (UKGC-authorised), distinct from financial spread betting platforms (FCA-regulated). Both deliver tax-free returns under separate UK regulatory frameworks. Betfair falls under gambling classification; spread betting falls under financial speculation — both tax-free, separate regulators.
- Can spread betting firms offer political prediction markets?
- Certain operators do — IG Index and Spreadex provide election outcome spread bets (e.g. "Conservative seats at 200–210"). These qualify for tax-free treatment. Market selection remains substantially narrower compared to Polymarket's 249 UK-relevant political contracts.
- Is there a UK prediction market with leverage?
- Not conventionally. Betfair and Smarkets operate on binary mechanics (stake only). Polymarket operates on binary mechanics. For leveraged event exposure, financial spread betting represents the sole FCA-regulated pathway — though it covers only financial instrument valuations, excluding specific event outcomes.