S&P 500 (SPX) Up or Down on July 24?

Platform comparison

Market context

Polymarket is currently pricing this contract at **94% YES**, which implies traders think the S&P 500 is very likely to finish **higher** than its previous trading-day close by the 20:00 UTC settlement cut-off. On Polymarket, that view is expressed through **USDC**-denominated shares on **Polygon**, with the outcome ultimately determined by the official SPX closing level rather than intraday moves.

That high probability sits in the context of a market that has already absorbed a sharp risk-off session. Saxo said the **S&P 500 fell 1.21% on Thursday** to 7,408.30, its worst day in a month, after oil spiked and AI-valuation concerns hit sentiment.[2] Moomoo’s Friday briefing described US equity futures as **slightly higher** early in the day, with S&P 500 futures about **+0.2%** as crude eased back below $100, which is consistent with why a “Up” outcome can still command a very high implied probability even after a weak prior close.[3]

For traders, the main dependencies are the same ones that have been moving the index all week: **oil**, **tariff fallout**, Middle East and Red Sea developments, and any surprise in global PMI data or central-bank commentary.[1] The practical Polymarket angle is that this is a same-day close-versus-prior-close contract, so late-session reversals matter more than the morning tone; if headlines stabilise energy and bond markets, the SPX can still finish above the prior close even after a volatile start.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Kalshi UK, which mirrors the Polymarket order book directly.

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.

FAQ

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.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.