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

Platform comparison

Market context

On Monday, 10 August 2026, traders will discover whether the S&P 500 closed higher or lower than Friday's close. A YES share pays out if the index rises; a NO share pays out if it falls. The current crowd-implied probability of 36% for an up day reflects modest pessimism, suggesting the market expects a decline more often than not over the coming weeks. This is a straightforward directional bet on a single day's performance, settled against the official closing price published by the exchange.

Daily moves in the S&P 500 have historically favoured upward days slightly—roughly 52–53% of trading days close higher than their predecessor over multi-year periods. The 36% YES probability therefore sits below that long-term baseline, indicating the crowd perceives headwinds specific to early August 2026 or broader market sentiment tilted toward caution. Comparable single-day markets on major indices typically see probabilities cluster between 45–55% absent significant scheduled events, so the current skew warrants attention to what catalysts might be driving the bearish lean.

The week of 10 August falls outside the typical earnings season, but traders should monitor any Federal Reserve communications, employment data revisions, or corporate guidance released in late July that might carry through into the following week. Geopolitical developments, yield movements in Treasury markets, and sector-specific news—particularly in technology, which dominates the index—can shift sentiment overnight. Market volatility indices and options positioning in the days immediately before settlement will offer real-time signals of trader conviction.

Methodology

This page reviews S&P 500 (SPX) Up or Down on August 10? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Prediction Market UK, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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 Prediction Market UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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%.