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.
For UK-based traders, two primary avenues exist to capitalise on accurate outcome forecasting: spread betting (through FCA-licensed financial spread betting operators) and prediction markets (through Polymarket, Betfair Exchange, or Smarkets). Grasping these distinctions is essential for both tax efficiency and tactical decision-making.
What Is Spread Betting in the UK?
The UK's FCA-authorised spread betting providers—including IG, CMC Markets, and Spreadex—allow you to stake a fixed sum per point shift in a financial asset (FTSE 100, currency pairs, individual equities). The defining features are:
- Leverage: Ranges from 2:1 to 20:1 based on the underlying asset category
- 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: Restricted to financial instruments (equity indices, currency markets, raw materials, equities) — excludes political or sporting contests
- Bid-ask spread: Embedded cost structure (usually 1–3 pips on major currency pairs)
What Are Prediction Markets?
Prediction markets enable you to acquire YES/NO binary contracts tied to tangible 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 both Capital Gains Tax and Income Tax in the UK, provided the account is held with an FCA-authorised spread betting operator. This represents one of the most advantageous tax positions available to UK retail traders. HMRC's published guidance on financial spread betting corroborates this treatment.
Betfair Exchange / Smarkets: Tax-Free
Winnings from UKGC-licensed betting exchanges enjoy identical tax-free status — categorised as gambling revenue under the Gambling Act 2005. Consequently, Betfair and Smarkets deliver the optimal combination: prediction market functionality alongside unambiguous tax-free treatment.
Polymarket: Tax Uncertain
Polymarket returns do not neatly align with either the gambling exemption (lacking UKGC authorisation) or the spread betting exemption (not an FCA-authorised financial spread betting platform). HMRC could classify them as CGT or Income Tax liabilities. Consult 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 assets (FTSE 100, currency pairs)
- Tax-free status is paramount and regulatory certainty is essential
- Your focus is on financial price dynamics rather than discrete event outcomes
- You require FCA-mandated negative balance safeguards
Choose Prediction Markets When:
- You possess demonstrable skill in predicting particular real-world occurrences (referendums, athletic contests, scientific breakthroughs)
- You prefer a bounded-loss, binary framework (maximum loss equals your stake)
- You need exposure to contract categories unavailable through spread betting (electoral politics, blockchain-based events, meteorological outcomes)
- Minimising expenses relative to conventional betting operators matters significantly
Best Combined Approach for UK Traders:
- Maintain an FCA-regulated spread betting account (IG, CMC) for financial asset exposure where leverage and tax-free treatment are strategically important
- Employ Smarkets or Betfair Exchange for UK electoral and sporting markets — UKGC-authorised, tax-free, GBP-denominated
- Access Polymarket via PolyGram for specialised markets absent from other venues (8,000+ international event contracts) — acknowledging tax ambiguity or maintaining thorough documentation
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-authorised). Both deliver tax-free returns under separate UK legal frameworks. Betfair falls under gambling classification; spread betting falls under financial speculation — both tax-free, overseen by different regulators.
- Can spread betting firms offer political prediction markets?
- Certain operators do — IG Index and Spreadex provide election outcome spread contracts (e.g. "Conservative seats at 200–210"). These returns are tax-free. Nevertheless, the selection remains substantially narrower than Polymarket's 249 UK-related electoral markets.
- Is there a UK prediction market with leverage?
- Not conventionally. Betfair and Smarkets operate on binary principles (stake only). Polymarket functions identically. For leveraged event exposure, FCA-regulated financial spread betting represents the sole authorised mechanism — though it exclusively covers financial instrument valuations, not specific event outcomes.