S&P 500 (SPX) Up or Down on August 7?

Platform comparison

Market context

Polymarket is pricing this S&P 500 close as **95% Up** today, with the contract settled in USDC on Polygon through conditional tokens, so the market is effectively saying the index is very likely to finish Friday above the prior trading day’s close. The reference point is the official SPX close on the most recent trading session, which was 7,723.55 on Wednesday after the index fell 0.3%; that makes today’s print a straight day-over-day comparison rather than a forecast of an absolute level.[1][11][18]

The probability sits well above what recent tape action alone would justify in a normal session, because SPX has been choppy: it fell 0.4% on Tuesday and 0.3% on Wednesday, yet still closed near record territory, and it has been roughly flat to slightly weaker over the past week and month in some data sets.[11][1][3][13] That kind of positioning means a 95% “Up” price is less about a calm equity backdrop and more about the market expecting the index to avoid an unusually large late-session reversal. For comparison, the index has also been making fresh highs this summer, so a small positive close would be consistent with the broader trend even if daily momentum has cooled.[10][16]

The main catalyst to watch is the July nonfarm payrolls and unemployment release, scheduled before the open on Friday, which can move Treasury yields, rate-cut expectations and therefore the cash index by the close.[10] Traders also need to watch whether any pre-market weakness in futures is carried through the open, because this market resolves on the official SPX cash close, not on intraday highs or the futures price. A higher or lower settlement will depend on whether the afternoon equity bid can absorb any macro surprise and preserve the final print above Thursday’s close.[17][18]

Sources: 1 · 2 · 3 · 4 · 5

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

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.

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%.