US Open, Qualification WTA: Katie Swan vs Mary Stoiana

Platform comparison

Market context

Katie Swan and Mary Stoiana are set for a US Open women’s qualifying match that was scheduled for 26 August at Flushing Meadows. Swan entered off a straight-sets win over Katrina Scott, while Stoiana, seeded 17th in the qualifying draw, had already advanced through her opening round, so this is a live tournament pairing rather than a speculative one-off. The crowd price at 0% YES is therefore a clear outlier against a match that has been on the schedule and tracked by the tournament draw.

For market-readers, the closest comparable cases are standard Grand Slam qualifying spots where the signal comes from draw placement, completed first-round results, and whether the scheduled court slot actually holds. Swan’s profile is less protected by seeding, but her recent form in New York was firm enough to reach this round, while Stoiana’s seeding and higher ranking make her the more model-friendly favourite. In programmatic terms, this is the sort of market that should be checked against live order-of-play feeds, completed scoreboards, and any draw updates before assuming the pre-match price is still valid.

The key catalysts are whether the match is officially started, delayed, moved, or completed within the settlement window, because a non-start or abandonment can push resolution away from a simple winner call. Traders watching via automation should flag tournament schedule changes, court assignments, and live score state, since qualifying matches can be rescheduled in tight weather or court-usage windows at the US Open. The latest published listings had the fixture on Court 11, with independent score pages showing it as an active qualifying match on 26 August.

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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 Polymarket Bot UK, which mirrors the Polymarket order book directly.

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

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 Polymarket Bot 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%.