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're a UK-based trader, you have two primary pathways to capitalise on accurate forecasts of future events: spread betting (through FCA-licensed financial spread betting operators) and prediction markets (through platforms such as Polymarket, Betfair Exchange, or Smarkets). Grasping these distinctions is essential for effective tax management and optimal strategy selection.
What Is Spread Betting in the UK?
In the UK, FCA-regulated entities such as IG, CMC Markets, and Spreadex provide financial spread betting services. You place wagers based on point fluctuations in financial assets (FTSE 100, currency pairs, individual equities). Defining characteristics include:
- Leverage: Usually ranges from 2:1 to 20:1 contingent on the asset category
- Tax-free profits: Spread betting is legally categorised as gambling in the UK — profits remain untaxed, and losses cannot be claimed as deductions
- FCA regulated: Comprehensive investor safeguards, mandatory negative balance protection
- Markets: Financial products (equity indices, currency markets, raw materials, equities) — excludes political or sporting events
- Bid-ask spread: Embedded expense (usually 1–3 pips on primary currency pairs)
What Are Prediction Markets?
Prediction markets enable you to acquire YES/NO binary contracts tied to tangible real-world events. The most prominent 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
In the UK, all spread betting returns are exempt from both Capital Gains Tax and Income Tax provided your account is held with an FCA-authorised spread betting provider. This represents one of the most advantageous tax positions available to UK retail investors. HMRC has formally documented this stance in their published materials on financial spread betting.
Betfair Exchange / Smarkets: Tax-Free
Winnings from UKGC-licensed betting exchanges are similarly tax-exempt — categorised as gambling proceeds under the Gambling Act 2005. This positions Betfair and Smarkets as offering the optimal combination: prediction market functionality WITH unambiguous 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 provider). HMRC could classify them as CGT or Income Tax liabilities. Consult our UK tax guide for detailed analysis.
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 treatment is critical and regulatory clarity 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 forecasting particular real-world occurrences (political contests, athletic competitions, scientific developments)
- You favour a loss-capped, binary framework (maximum loss equals your stake)
- You need access to event categories unavailable through spread betting (political races, blockchain developments, meteorological outcomes)
- Reduced costs relative to conventional betting operators matter significantly
Best Combined Approach for UK Traders:
- Deploy an FCA-authorised spread betting account (IG, CMC) for financial instrument positions where leverage and tax exemption are priorities
- Deploy Smarkets or Betfair Exchange for UK political and sports markets — UKGC-authorised, tax-free, GBP-denominated
- Deploy Polymarket via PolyGram for niche markets with no alternative (8,000+ worldwide event contracts) — while managing tax implications 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-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-exempt, overseen by different authorities.
- Can spread betting firms offer political prediction markets?
- Certain providers do — IG Index and Spreadex provide election outcome spread positions (e.g. "Conservative seats at 200–210"). These remain tax-free. Nevertheless, selection is substantially narrower than Polymarket's 249 UK-focused political markets.
- Is there a UK prediction market with leverage?
- Not conventionally. Smarkets and Betfair operate as binary (stake-only). Polymarket functions as binary. For leveraged event exposure, financial spread betting represents the sole FCA-authorised option — though it exclusively covers financial instrument valuations, not discrete event outcomes.