Key takeaway: Kalshi's fee structure is transparent but not always the cheapest option for UK traders. Most UK-based prediction markets charge 2–5% in total costs (spread + fees), whilst Kalshi typically sits at 3–4%. This guide compares real fee schedules across major platforms to help you calculate your true cost of trading.
Understanding Prediction Market Fees: The Hidden Costs
When you trade on a prediction market, the headline price you see isn't the full story. Unlike traditional stock exchanges, prediction markets bundle costs in ways that can surprise newcomers. You'll encounter spreads (the gap between buy and sell prices), platform fees, settlement fees, and sometimes withdrawal charges. Kalshi, the US-regulated prediction market, has gained attention from UK traders, but understanding how its costs stack up against local alternatives is essential before committing capital.
The total cost of a trade isn't simply a percentage fee—it's the combination of what you pay to enter a position and what you lose when you exit. A 2% spread plus a 1% platform fee means you're already 3% underwater before the market even moves in your favour. Over dozens of trades, these costs compound dramatically.
Kalshi's Fee Structure Explained
Kalshi operates under US Commodity Futures Trading Commission (CFTC) regulation and offers a relatively straightforward fee model. The platform charges no account fees and no deposit or withdrawal charges for standard bank transfers. However, this simplicity masks the real cost: the spread.
On Kalshi, spreads vary by contract liquidity. High-volume contracts (such as US election outcomes or major economic indicators) typically have spreads of 1–2%, meaning the difference between the best buy price and best sell price is 1–2% of the contract value. Lower-volume contracts can see spreads of 5–10% or wider. When you buy a contract at the ask price and immediately sell at the bid price, you lose that spread—your true entry cost.
Kalshi also charges a settlement fee of 0.5% on the final value of your position when you close it or when the contract settles. This is a flat cost applied to all trades, regardless of profit or loss. So a £1,000 position costs you £5 to settle, plus whatever spread you paid to enter.
For a typical round-trip trade on a liquid Kalshi contract:
- Entry spread: 1–2%
- Exit spread: 1–2%
- Settlement fee: 0.5%
- Total cost: 2.5–4.5%
This assumes you're trading popular contracts. Niche markets can cost significantly more.
UK Prediction Market Alternatives: Fee Comparison
Several platforms operate legally in the UK or serve UK customers with varying fee structures. Here's how they compare:
Betfair Exchange (Prediction Markets)
Betfair, primarily known as a betting exchange, has expanded into structured prediction markets. The platform charges a commission of 2–5% on net winnings (not on total stake). This is significantly cheaper than Kalshi for winning trades but offers no rebate on losses. Betfair's spreads are typically tighter than Kalshi's on popular markets because of higher liquidity from the betting community.
For a £1,000 winning bet at 2% commission, you pay £20. For a loss, you pay nothing. This asymmetric fee structure favours profitable traders but punishes those with losing streaks.
Smarkets
Smarkets is a UK-regulated exchange that operates similarly to Betfair. It charges 2% commission on net winnings, with no fees on losses. Smarkets has historically offered some of the tightest spreads in the UK prediction market space, particularly on political events and major sporting outcomes. The platform is FCA-regulated, which provides UK-specific consumer protections.
PredictIt (US-based, accessible to UK users)
PredictIt charges a flat 10% fee on net winnings when you cash out. This is substantially higher than Kalshi or UK-based alternatives. However, PredictIt specialises in niche political markets with unique contracts unavailable elsewhere. The high fee is the trade-off for access to specialised markets.
Polymarket (Ethereum-based, decentralised)
Polymarket operates on blockchain infrastructure and charges 2% on trades plus variable gas fees (typically £2–£20 depending on network congestion). For UK users, this introduces additional complexity: you must hold cryptocurrency, navigate wallet management, and account for potential tax implications. The 2% fee is competitive, but hidden costs in currency conversion and gas fees can push total costs to 3–5%.
Real-World Cost Examples: Kalshi vs Alternatives
Let's walk through three realistic trading scenarios to see how fees actually impact your returns.
Scenario 1: £1,000 Winning Trade on a Liquid Market
Kalshi:
- Buy at 55 (cost: £550 + 1.5% spread = £558.25)
- Sell at 75 (proceeds: £750 – 1.5% spread = £738.75)
- Settlement fee on £750: £3.75
- Net profit: £738.75 – £558.25 – £3.75 = £176.75 (17.7% return on £1,000 risked)
Betfair (2% commission):
- Stake: £1,000
- Winnings: £1,500 (assuming 1.5 odds)
- Net profit: £500
- Commission on £500: £10
- Net profit: £490 (49% return)
In this scenario, Betfair is dramatically cheaper because you only pay commission on winnings. Kalshi's spread-based model costs more on winning trades.
Scenario 2: £1,000 Losing Trade
Kalshi:
- Buy at 45 (cost: £450 + 1.5% spread = £456.75)
- Sell at 25 (proceeds: £250 – 1.5% spread = £246.25)
- Settlement fee on £250: £1.25
- Net loss: £456.75 + £1.25 – £246.25 = –£211.75 (21.2% loss)
Betfair (2% commission):
- Stake: £1,000
- Loss: £1,000
- Commission: £0 (no fee on losses)
- Net loss: –£1,000 (100% loss)
On losing trades, Kalshi's settlement fee still applies, making losses slightly worse. Betfair charges nothing, so your loss is exactly your stake.
Scenario 3: High-Volume Trader (20 trades per month)
Assuming an average trade size of £500 and a 50% win rate:
Kalshi (average 3.5% total cost per round trip):
- 10 winning trades: 10 × £500 × 3.5% = £175 in fees
- 10 losing trades: 10 × £500 × 3.5% = £175 in fees
- Monthly cost: £350
Betfair (2% commission on wins only):
- 10 winning trades: 10 × £500 × 2% = £100 in fees
- 10 losing trades: £0
- Monthly cost: £100
For active traders, Betfair's win-only commission model saves substantial money over time, assuming you maintain a positive win rate.
Hidden Costs and Considerations Beyond Base Fees
Raw fee percentages don't tell the complete story. Several other factors affect your true cost of trading:
Liquidity and Slippage
Kalshi's spreads are only guaranteed if you accept the market price instantly. If you place a limit order and wait for it to fill, you might miss the market entirely. On illiquid contracts, the spread can widen dramatically, turning a 2% cost into a 10% cost. UK alternatives like Betfair and Smarkets generally have deeper liquidity on major events, reducing slippage risk.
Currency Conversion
Kalshi operates in US dollars. UK traders must convert pounds to dollars (and back), incurring FX fees typically of 1–2% depending on your bank or payment provider. This is a hidden cost not advertised by Kalshi. Betfair and Smarkets operate in pounds, eliminating this cost entirely.
Minimum Bet Sizes
Kalshi's minimum contract size is £1 (or $1 equivalent), making it accessible to small traders. Betfair and Smarkets also allow small stakes, but some niche markets have higher minimums. This affects whether you can efficiently diversify small amounts across multiple positions.
Tax Implications
In the UK, betting exchange winnings are generally tax-free (under betting duty rules), whilst investment-style trading may trigger capital gains tax. Kalshi's structure is closer to investment trading, potentially exposing UK users to tax liabilities that Betfair users wouldn't face. You should consult a tax advisor to understand your specific situation.
Choosing the Right Platform: A Decision Framework
No single platform is cheapest for all traders. Your choice depends on your trading style:
Choose Kalshi if:
- You want access to US-regulated, CFTC-supervised contracts
- You're trading niche markets unavailable elsewhere
- You're comfortable with US dollar exposure
- You plan to hold positions long-term (fees matter less per trade)
Choose Betfair or Smarkets if:
- You're an active trader with a positive win rate
- You want to trade in pounds without FX costs
- You prefer FCA regulation and UK consumer protections
- You're interested in political or sporting prediction markets
Choose Polymarket if:
- You're comfortable with cryptocurrency and blockchain technology
- You want access to decentralised, uncensored markets
- You're willing to accept higher operational complexity
- You're making infrequent, large trades (fixed gas fees matter less)
Frequently Asked Questions
Does Kalshi charge any hidden fees I should know about?
Kalshi's main fees are transparent: spreads and the 0.5% settlement fee. However, currency conversion fees (if you're a UK user) and potential tax implications aren't advertised by Kalshi itself. Always account for FX costs when comparing to pound-based platforms.
Can I negotiate fees on prediction markets?
Most prediction markets don't negotiate individual fees. However, some platforms (particularly Polymarket and Betfair) offer loyalty rebates or volume discounts for high-frequency traders. Check each platform's current promotions.
Are prediction market fees tax-deductible?
In the UK, betting exchange fees are generally not tax-deductible because betting winnings are tax-free. If you're trading on Kalshi and subject to capital gains tax, fees may be deductible as trading costs. Consult a tax professional for your specific circumstances.
Which platform has the tightest spreads?
Betfair and Smarkets typically have the tightest spreads on major political and sporting events due to high liquidity. Kalshi's spreads vary by contract; popular markets are competitive, but niche contracts can be wide. Polymarket's spreads depend on liquidity pools, which vary significantly.
Is there a fee-free prediction market?
No legitimate regulated prediction market is completely free. All charge fees in some form—either as spreads, commissions, or settlement charges. Beware of platforms claiming zero fees; they may be unregulated or use other revenue models (like selling user data).
How do I calculate my true cost per trade?
Add entry spread + exit spread + any platform fees + settlement fees + currency conversion costs (if applicable). For a £1,000 trade on Kalshi: 1.5% + 1.5% + 0.5% + 1.5% (FX) = 5% total, or £50. Compare this to Betfair's 2% commission on winnings (£20 if you win) to see which is cheaper for your specific trade.
Final Thoughts: Making Your Fee Comparison
Prediction market fees are a critical factor in long-term profitability, yet many traders focus only on the market outlook and ignore costs. A Kalshi Alternative UK comparison reveals that no single platform dominates on price—instead, the cheapest option depends on your trading frequency, win rate, market preferences, and risk tolerance.
Kalshi offers regulatory credibility and access to unique US markets, but UK-based alternatives like Betfair and Smarkets often provide lower total costs for active traders. Before opening an account, calculate your expected monthly costs using the scenarios above, and factor in currency conversion if you're trading cross-border.
For a comprehensive, independent breakdown of prediction market platforms and their true costs, visit Kalshi Alternative UK.