Cincinnati Open: Sloane Stephens vs Anastasia Potapova

Platform comparison

Market context

Sloane Stephens and Anastasia Potapova were scheduled to meet in Cincinnati on 16 August, and the market only resolves to one side if that player advances; if the match is not played, ends level, or drifts beyond the seven-day cut-off without a winner, it settles 50-50. A YES share here is simply a claim on Stephens advancing, while a NO share pays if Potapova advances.

The crowd-implied 100% YES price is best read as a sign of the market believing the outcome is effectively decided, but that can reflect either a completed result or a stale quote if trading has not updated promptly. In comparable tennis markets, the main driver of sudden repricing is not ranking alone but whether the match has already finished, been suspended, or moved within the order of play; one live scoreboard listed the match as final, while other pre-match pages had shown it as upcoming earlier on 16 August.

The key catalysts are therefore procedural rather than tactical: the official match status, any retirement or walkover news, and whether the Cincinnati schedule shifts because of weather or court delays. Reports and scoreboards indicated Champions’ Court as the venue and a hard-court second-round match, so the most relevant dependency is whether the tournament confirms completion before the settlement window closes on 23 August.

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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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%.