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 ways to profit from correctly forecasting outcomes: spread betting (via UKGC-licensed financial spread betting firms) and prediction markets (via Polymarket, Betfair Exchange, or Smarkets). Understanding the differences is critical for tax planning and strategy.
What Is Spread Betting in the UK?
Financial spread betting in the UK is offered by FCA-regulated firms like IG, CMC Markets, and Spreadex. You bet a amount per point movement in a financial instrument (FTSE 100, forex, individual stocks). Key characteristics:
- Leverage: Typically 2:1 to 20:1 depending on asset class
- Tax-free profits: Spread betting is legally classified as gambling in the UK — profits are tax-free, losses are not deductible
- FCA regulated: Full consumer protection, negative balance protection required
- Markets: Financial instruments (indices, forex, commodities, individual stocks) — not political or sports outcomes
- Bid-ask spread: Built-in cost (typically 1–3 pips on major forex pairs)
What Are Prediction Markets?
Prediction markets let you buy YES/NO binary contracts on real-world outcomes. Major UK-accessible options:
- 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 profits are exempt from Capital Gains Tax and Income Tax in the UK, provided you use an FCA-authorised spread betting account. This is one of the most significant tax advantages available to UK retail traders. HMRC confirmed this position in their guidance on financial spread betting.
Betfair Exchange / Smarkets: Tax-Free
UKGC-licensed betting exchange winnings are also tax-free — treated as gambling income under the Gambling Act 2005. This makes Betfair and Smarkets the best of both worlds: prediction market mechanics AND clear tax-free status.
Polymarket: Tax Uncertain
Polymarket winnings do not fall clearly into either the gambling exemption (no UKGC licence) or the spread betting exemption (not FCA-authorised financial spread betting). HMRC may treat them as CGT or Income Tax events. 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 want leveraged exposure to financial instruments (FTSE 100, forex)
- Tax-free status is non-negotiable and you want absolute clarity
- You're trading financial price movements, not event outcomes
- You want FCA negative balance protection
Choose Prediction Markets When:
- You have an edge in forecasting specific real-world events (elections, sports, science)
- You want a capped-loss, binary structure (max loss = stake)
- You want access to markets that don't exist in spread betting (politics, crypto events, weather)
- Lower fees than traditional bookmakers are a priority
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 matter
- 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 offer tax-free profits under different UK legal frameworks. 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.