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

Platform comparison

Market context

The S&P 500 is being judged on whether Friday’s official close finishes above the previous trading day’s close, so the market is effectively a one-day direction bet on the index rather than a broad trend call. The latest reported close before expiry was 7,503.85 on 7 August, after a 0.4% drop on Tuesday, while earlier in the week the index had already printed 7,482.71 on 8 July and traded within a relatively tight five-day band. [11][6][2]

A 96% crowd-implied probability for **YES** fits a backdrop where the index has been near record territory and has recently produced several strong sessions, including a 1.48% rise to 7,600.50, described as the second-highest close in history. That kind of positioning can make an “up” outcome look routine, but the last few sessions also show that small pullbacks are common even during strong tapes, so the final print still depends on whether buyers hold the index above the prior close into settlement. [9][7][11]

For traders, the main catalysts are the US labour-market releases due before the open, including nonfarm payrolls and the unemployment rate, which can move Treasury yields, equity index futures and, by extension, the cash close that determines settlement. In crypto-linked terms, the on-chain payoff is in USDC and the market can react first through S&P 500 futures, with any spillover from BTC and ETH risk sentiment likely to matter only if macro data shifts rate expectations sharply. [15][20]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically this overview focuses on on-chain pricing: Polymarket's live mid comes from the Polygon conditional-token order book and settles automatically in USDC. The other three venues — Kalshi, Betfair, Manifold — sit alongside as off-chain reference points so you can see how the contract translates across regulatory and settlement regimes.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

UK Frequently Asked Questions

Why USDC and not ETH or USDT?

USDC is the Polygon standard — audited reserves (Circle, monthly attestation), deepest order book, low gas costs. ETH volatility would distort probability quotes; USDT has thinner Polygon liquidity than USDC.

What does a transaction cost on Polygon?

Polygon gas is typically under $0.01 per transaction. A full trade cycle (Approve + Order + Fill) totals around $0.03 — compared to $5-50 on Ethereum mainnet.

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%.