National Bank Open: Marta Kostyuk vs Madison Keys

Platform comparison

Market context

Polymarket has this contract at **98% YES**, so the market is pricing Madison Keys to advance over Marta Kostyuk almost as a near-certainty rather than a coin flip. Because settlement is tied to the match result on the National Bank Open draw, buyers of YES are effectively taking exposure to Keys progressing, with the position held in USDC on Polygon through conditional tokens rather than a traditional sportsbook ticket.

The historical frame supports why the price is so one-sided. Keys has beaten Kostyuk in both of their previous completed meetings, including straight-sets wins at Wimbledon in 2023 and 2024[1][2][17]. The wider recent form data also leans Keys’ way: she has posted a stronger last-52-weeks win rate than Kostyuk in some trackers, and the head-to-head record is consistently listed as 2-0 or 3-0 for Keys depending on the database cut-off[1][2][7]. That makes the current quote look like a market that is anchoring heavily to prior match-up history rather than treating the pairing as close.

For traders, the main catalyst is simple: whether the match starts, finishes, and produces a clean winner before the settlement window closes. If the match is postponed, interrupted, or delayed beyond seven days without a winner, the contract can settle 50-50 under the rules, so scheduling updates matter as much as on-court performance. Live draw and fixture listings still show the Toronto/National Bank Open pairing, which means any withdrawal, walkover, or rescheduling would be the key event to watch rather than a broader tournament narrative[6][9][14].

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

UK Frequently Asked Questions

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.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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%.