Largest IPO by market cap in 2026?

Platform comparison

Market context

Polymarket is currently pricing this contract at **93% YES**, with settlement governed by USDC on Polygon through conditional tokens rather than a discretionary editor call. The practical question is which 2026 IPO finishes its first U.S. trading day with the highest dollar market capitalisation, using the official close and outstanding shares, so the market is really about first-day size, pricing discipline and aftermarket demand rather than the broader climate sector narrative.[6]

That high probability reflects how dominant the climate-tech IPO window has been so far. By early July, one dataset counted nine IPOs, seven of them energy businesses, and later reporting said the tally had risen further as Lime and Standard Nuclear came public; separate coverage of Fervo’s May debut described a $1.89 billion raise and roughly a $10 billion first-day valuation, while Fortune reported it closed day one at $36.54 a share.[1][2][7] For context, that shows the bar is already high: any later entrant would need either a much larger float or a stronger first-day pop to overtake the current leaders.[12][14]

The main catalysts are filing and pricing updates from the handful of climate names still likely to test public markets before year-end, plus any changes to listing schedules or share counts that alter the market-cap maths on day one. Bloomberg reported in July that the AI power boom had helped trigger the strongest rush into climate-tech deals since 2022, which matters because data-centre power demand is feeding investor appetite for geothermal, nuclear and grid-adjacent listings.[8] On Polymarket, that means traders are watching for S-1 amendments, pricing ranges, underwriter size-ups and exact first-trade dates: the contract resolves on the company with the largest official closing market cap, so even a modest divergence in share count or closing print can matter more than the headline raise.[6]

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

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

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.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

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%.