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.
As a UK trader, you have two distinct pathways to generate returns from accurately predicting outcomes: spread betting (via UKGC-licensed financial spread betting firms) and prediction markets (via Polymarket, Betfair Exchange, or Smarkets). Grasping these distinctions is essential for effective tax management and investment planning.
What Is Spread Betting in the UK?
Financial spread betting in the UK is delivered by FCA-regulated operators such as IG, CMC Markets, and Spreadex. You place a wager per point shift in a financial asset (FTSE 100, forex, individual stocks). Core attributes include:
- Leverage: Commonly 2:1 to 20:1 based on the underlying asset class
- Tax-free profits: Spread betting is legally treated as gambling in the UK — profits incur no tax, and losses cannot be offset
- FCA regulated: Comprehensive investor safeguards, mandatory negative balance protection
- Markets: Financial instruments (indices, forex, commodities, individual stocks) — not political or sports outcomes
- Bid-ask spread: Embedded cost (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. Leading UK-accessible platforms include:
- 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, as long as you trade through an FCA-authorised spread betting account. This represents one of the most valuable tax benefits available to UK retail investors. HMRC has explicitly endorsed this position in their official guidance on financial spread betting.
Betfair Exchange / Smarkets: Tax-Free
UKGC-licensed betting exchange returns are likewise tax-free — classified as gambling income under the Gambling Act 2005. This makes Betfair and Smarkets an optimal combination: prediction market mechanics AND transparent tax-free treatment.
Polymarket: Tax Uncertain
Polymarket returns do not neatly fit into either the gambling exemption (lacks UKGC licence) or the spread betting exemption (not an FCA-authorised financial spread betting provider). HMRC could treat them 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 exposure to financial instruments (FTSE 100, forex)
- Tax-free status is essential and you require regulatory certainty
- You're focused on trading financial price movements rather than discrete event outcomes
- You value FCA negative balance protection
Choose Prediction Markets When:
- You possess an edge in forecasting particular real-world events (elections, sports, science)
- You prefer a capped-loss, binary framework (maximum loss = stake)
- You need access to markets unavailable in spread betting (politics, crypto events, weather)
- Reduced fees relative to conventional bookmakers matter to your strategy
Best Combined Approach for UK Traders:
- Use an FCA-regulated spread betting account (IG, CMC) for financial instrument exposure where leverage and tax-free status are priorities
- Use Smarkets or Betfair Exchange for UK politics and sports — UKGC-regulated, tax-free, GBP
- Use Polymarket via PolyGram for markets that don't exist elsewhere (8,000+ global event contracts) — accepting the tax uncertainty or documenting it carefully
FAQ — Spread Betting vs Prediction Markets UK
- Is Betfair Exchange classed as spread betting?
- No — Betfair Exchange is a betting exchange (UKGC-regulated), not a financial spread betting platform (FCA-regulated). Both deliver tax-free returns under distinct UK legal structures. Betfair is classified as gambling; spread betting is classified as financial speculation — both tax-free, different regulators.
- Can spread betting firms offer political prediction markets?
- Some do — IG Index and Spreadex offer election outcome spread bets (e.g. "Conservative seats at 200–210"). These are tax-free. However, coverage is much more limited than Polymarket's 249 UK-relevant political markets.
- Is there a UK prediction market with leverage?
- Not in the traditional sense. Betfair and Smarkets are binary (stake only). Polymarket is binary. For leveraged event trading, financial spread betting is the only FCA-regulated route — but only covers financial instrument prices, not discrete event outcomes.