National Bank Open: Marta Kostyuk vs Iga Swiatek

Platform comparison

Market context

Polymarket is pricing Marta Kostyuk to advance against Iga Swiatek at **8% YES**, which translates into a strong lean towards **Swiatek** on the contract’s conditional-token, USDC-settled market. For traders, the key point is not just who is favoured on the court, but how the market resolves: if the match is not completed in the required way, or is pushed out beyond the seven-day window, the contract can settle **50-50** rather than on a winner.[4]

That low price sits well below the broader betting and model consensus around the same fixture. Recent previews and price boards have had Swiatek as the favourite, with sportsbook lines around -140 to -150 and model probabilities in the high-60s to low-70s, although one recent Action Network preview took the opposite view and backed Kostyuk on the moneyline.[2][5][6][12] Tennis Tonic also leaned Swiatek, projecting a three-set win, while Tennis.com’s tournament page listed Swiatek as the projected winner at 57%.[1][8] For a Polymarket user, that gap matters because a single sharp disagreement can create liquidity, but the contract still pays only on the actual advance outcome.

The main catalysts are scheduling and match completion. The match was originally set for August 9 in Toronto, and the market’s settlement logic makes draw-state changes, walkovers, cancellations and stoppages immediately relevant to pricing.[4] Traders should watch the official order of play, any late injury or withdrawal notes, and whether the match starts and finishes cleanly within the settlement rules, because an incomplete match can still force a neutral resolution even if one player appears ahead on court.[4]

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 PolyGram, which mirrors the Polymarket order book directly.

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

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 PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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%.