S&P 500 (SPX) Up or Down on August 10?

Platform comparison

Market context

The S&P 500 will either close higher or lower on Monday, 10 August 2026 compared to its previous trading day's close. The 26% crowd probability for an up day reflects a bearish lean, suggesting market participants expect downward pressure or consolidation heading into mid-August. This positioning matters for algorithmic traders building conditional orders around weekend risk events or for those running copy-trading strategies that require directional conviction before committing capital.

Historical equity behaviour in early-to-mid August shows mixed patterns. The "summer doldrums" period typically features lower volumes and wider intraday swings, though directional bias varies year to year depending on earnings season tail-end effects and macroeconomic data releases. In 2025, the S&P 500 experienced volatility around Fed communications and inflation prints during similar windows. A 26% up probability sits below the historical 50% baseline, suggesting the crowd is pricing in either negative overnight developments from Asia-Pacific markets or anticipating a specific data release or corporate announcement on the day itself.

Traders should monitor Friday's close (9 August) for any late-session momentum, as well as any pre-market news from earnings reports or economic data scheduled for Monday morning. Conditional order logic would typically hinge on overnight futures performance and opening gap direction. The settlement window closes at 20:00 GMT, giving traders the full US trading session to assess whether the close will exceed or fall short of the prior day's level. For bot-based strategies, the key variable is whether any scheduled announcements—such as retail sales or jobless claims data—land before or after market open, as this affects the probability distribution throughout the session.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

UK Frequently Asked Questions

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Polymarket Bot UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.