Plus500, the FTSE 250 online trading group, has become the first broker outside Kalshi's own to offer a new type of futures contract on Kalshi's US exchange.
The contracts are called perpetual futures, or "perps".
A normal futures contract is a bet on where a price will be on a set date, and it ends when that date arrives.
Perps have no end date, so traders can hold a position for as long as they like without having to renew it.
Perps have long traded on offshore crypto platforms, outside US regulation.
Kalshi, a US exchange regulated by the Commodity Futures Trading Commission (CFTC), launched the first regulated perps contract in May.
It has since added versions tied to cryptocurrencies, commodities and stock indices.
What Plus500 does
Plus500 is what is known as a futures commission merchant (FCM), a firm that lets customers place trades on an exchange and handles the processing behind the scenes.
It runs execution, clearing, which means settling trades, and risk management on its own technology.
The perps are available through its business-to-business channels, which supply trading services to partner firms and their customers.
Plus500 already offers Kalshi's prediction markets, where users trade on the outcome of real-world events.
Why it matters
The company said the launch widens its product range and deepens its presence in the US.
It plans to add more perps as Kalshi lists them, and says it wants to win early market share in a fast-growing area.
David Zruia, Plus500's chief executive, said the US business could roll out new products "at speed".
No financial details were given.
