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 face a choice between two separate pathways to generate returns from accurate event forecasting: spread betting (through FCA-licensed financial spread betting operators) and prediction markets (through Polymarket, Betfair Exchange, or Smarkets). Grasping these distinctions matters significantly for your tax position and overall approach.
What Is Spread Betting in the UK?
The UK's financial spread betting sector is overseen by the FCA and includes operators such as IG, CMC Markets, and Spreadex. You stake a fixed amount per point shift in a financial asset (FTSE 100, currency pairs, individual equities). Core features include:
- Leverage: Commonly ranges from 2:1 to 20:1 based on the underlying asset
- Tax-free profits: Spread betting is legally treated as gambling in the UK — gains incur no tax, and losses cannot be written off
- FCA regulated: Comprehensive investor safeguards, mandatory negative balance protection
- Markets: Financial instruments (indices, currencies, commodities, equities) — excludes political or sports events
- Bid-ask spread: Inherent expense (usually 1–3 pips on major currency pairs)
What Are Prediction Markets?
Prediction markets enable you to trade binary YES/NO contracts pegged to actual real-world events. The primary UK-accessible platforms are:
- Polymarket (via PolyGram): 8,400+ markets, USDC-based, ~1% effective fee, legally ambiguous
- Betfair Exchange: 500 markets, sterling-denominated, 5% commission, UKGC licensed
- Smarkets: 200 markets, sterling-denominated, 2% commission, UKGC licensed
Tax Treatment — The Critical Difference
Spread Betting: Tax-Free
Every pound of spread betting gain is free from Capital Gains Tax and Income Tax in the UK, assuming you operate through an FCA-authorised spread betting account. This represents one of the strongest tax incentives available to UK retail investors. HMRC's official position on financial spread betting confirms this status.
Betfair Exchange / Smarkets: Tax-Free
Winnings on UKGC-licensed betting exchanges carry no tax liability — classified as gambling income under the Gambling Act 2005. This positions Betfair and Smarkets as ideal hybrids: prediction market functionality PLUS explicit tax-free certainty.
Polymarket: Tax Uncertain
Polymarket gains sit in a grey area: they don't qualify for the gambling exemption (lacks UKGC authorisation) nor the spread betting exemption (not an FCA-authorised financial spread betting service). HMRC could classify 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 positions in financial instruments (FTSE 100, currency pairs)
- Tax-free treatment is essential and you need regulatory certainty
- Your focus is on financial price shifts rather than discrete event outcomes
- You value FCA negative balance safeguards
Choose Prediction Markets When:
- You possess genuine insight into forecasting particular real-world events (referendums, athletic competitions, scientific breakthroughs)
- You prefer a bounded-loss, binary framework (maximum loss equals your stake)
- You need access to events unavailable through spread betting (geopolitics, emerging tech, meteorological events)
- Reduced fees relative to conventional betting operators matter to your strategy
Best Combined Approach for UK Traders:
- Employ an FCA-regulated spread betting account (IG, CMC) for financial instrument exposure where leverage and tax-free gains are priorities
- Employ Smarkets or Betfair Exchange for UK sports and political events — UKGC-regulated, tax-free, sterling-based
- Employ Polymarket via PolyGram for niche markets absent elsewhere (8,000+ global event contracts) — accepting 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 but operate under separate UK legal regimes. Betfair falls under gambling law; spread betting falls under financial speculation — both tax-exempt, different supervisors.
- 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 remain tax-free. Nonetheless, their event selection pales in comparison to Polymarket's 249 UK-focused political contracts.
- Is there a UK prediction market with leverage?
- Not conventionally. Betfair and Smarkets operate as binary instruments (stake only). Polymarket functions similarly. To access leveraged event trading, financial spread betting represents the sole FCA-regulated option — though it covers only financial instrument valuations, not specific event outcomes.