National Bank Open: Marta Kostyuk vs Iga Swiatek

Platform comparison

Market context

Iga Swiatek and Marta Kostyuk are set to meet in the National Bank Open, and the market will pay out on who actually advances from the match. In prediction-market terms, a **YES** share here means Kostyuk advances, while a **NO** share means Swiatek advances; if the match is not completed within the market’s rules, the outcome can fall back to 50-50.

The current 44% YES price suggests the market is treating Kostyuk as a live underdog rather than a clear favourite. That fits the head-to-head record: Swiatek leads the rivalry 4-1 in one data set and 3-0 in several others, with Swiatek also winning their most recent completed meeting at the 2026 French Open after earlier hard-court wins in Cincinnati 2024 and Indian Wells 2024.[2][3][4] For a new reader, that means the price is not just a forecast of who is “better” overall, but of how likely Kostyuk is to win this specific encounter under the tournament conditions.

Traders should watch the official draw order, any schedule changes, and whether either player is carrying fitness issues or withdrawing before first serve, because those are the main paths to a voided or reshaped market. The settlement window runs past the original match slot, so a delay of more than seven days without a winner would push the market to 50-50 under the stated rules. Live score services were already listing the match for 8 August 2026, which means the key catalyst is simply whether play begins and finishes normally or whether weather, scheduling, or injury changes the outcome path.[6][9]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews National Bank Open: Marta Kostyuk vs Iga Swiatek across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Prediction Market UK, which mirrors the Polymarket order book at 0% fees.

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%.