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.
If you trade in the UK, you have two primary avenues for generating returns through accurate outcome forecasting: spread betting (available through UKGC-licensed financial spread betting operators) and prediction markets (accessible via Polymarket, Betfair Exchange, or Smarkets). Grasping these distinctions is essential for effective tax management and decision-making.
What Is Spread Betting in the UK?
The UK's financial spread betting sector is served by FCA-regulated providers including IG, CMC Markets, and Spreadex. You stake a sum per point shift in a financial asset (FTSE 100, forex, individual stocks). Essential features include:
- Leverage: Commonly ranges from 2:1 to 20:1 based on the underlying asset
- Tax-free profits: Financial spread betting is legally treated as gambling in the UK — returns are tax-exempt, and losses cannot be claimed as deductions
- FCA regulated: Comprehensive investor safeguards, mandatory negative balance protection
- Markets: Financial products (indices, forex, commodities, equities) — excludes political or sports predictions
- Bid-ask spread: Embedded expense (usually 1–3 pips on major forex pairs)
What Are Prediction Markets?
Prediction markets enable you to acquire YES/NO binary contracts on actual real-world events. The primary UK-accessible platforms are:
- Polymarket (via PolyGram): 8,400+ markets, crypto (USDC), ~1% effective fee, grey zone legally
- Betfair Exchange: 500 markets, GBP, 5% commission, UKGC licensed
- Smarkets: 200 markets, GBP, 2% commission, UKGC licensed
Tax Treatment — The Critical Difference
Spread Betting: Tax-Free
All spread betting returns are exempt from Capital Gains Tax and Income Tax in the UK, provided you operate through an FCA-authorised spread betting provider. This represents one of the most valuable tax benefits accessible to UK retail investors. HMRC has formally documented this treatment in their published guidance on financial spread betting.
Betfair Exchange / Smarkets: Tax-Free
Winnings from UKGC-licensed betting exchanges are likewise tax-exempt — classified as gambling income under the Gambling Act 2005. This positions Betfair and Smarkets as an optimal solution: prediction market functionality combined with transparent tax-free treatment.
Polymarket: Tax Uncertain
Polymarket returns do not neatly fit either the gambling exemption (lacks UKGC authorisation) or the spread betting exemption (not an FCA-authorised financial spread betting service). HMRC could potentially classify them as CGT or Income Tax liabilities. See our prediction markets 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 assets (FTSE 100, forex)
- Tax-free treatment is paramount and regulatory certainty is essential
- Your focus is on financial price dynamics rather than discrete event outcomes
- You require FCA negative balance safeguards
Choose Prediction Markets When:
- You possess demonstrable skill in forecasting particular real-world occurrences (elections, sports, scientific outcomes)
- You prefer a bounded-loss, binary framework (maximum loss = initial stake)
- You need access to markets unavailable through spread betting (political events, digital asset outcomes, meteorological forecasts)
- Competitive pricing relative to conventional bookmakers matters significantly
Best Combined Approach for UK Traders:
- Employ an FCA-regulated spread betting account (IG, CMC) for financial instrument positions where leverage and tax-free returns are crucial
- Employ Smarkets or Betfair Exchange for UK political and sporting events — UKGC-regulated, tax-free, GBP-denominated
- Employ Polymarket via PolyGram for specialised markets with limited availability elsewhere (8,000+ international event contracts) — acknowledging the tax ambiguity or maintaining thorough records
FAQ — Spread Betting vs Prediction Markets UK
- Is Betfair Exchange classed as spread betting?
- No — Betfair Exchange operates as a betting exchange (UKGC-regulated), distinct from financial spread betting platforms (FCA-regulated). Both deliver tax-free returns under separate UK regulatory structures. Betfair falls under gambling classification; spread betting falls under financial speculation — both tax-exempt, governed by different authorities.
- Can spread betting firms offer political prediction markets?
- Some do — IG Index and Spreadex provide election outcome spread bets (e.g. "Conservative seats at 200–210"). These returns are tax-free. Market availability remains considerably narrower than Polymarket's 249 UK-focused political contracts.
- Is there a UK prediction market with leverage?
- Not conventionally. Betfair and Smarkets operate on binary terms (stake only). Polymarket functions as binary. For leveraged event speculation, financial spread betting represents the sole FCA-regulated option — though it covers only financial instrument prices, not specific event outcomes.