Prediction market platform Polymarket has surpassed $1.8 billion in annualized revenue, the company told CNBC on Tuesday.

That's up from June, when Polymarket disclosed that its annual revenue run rate was north of $1 billion, following the launch of its domestic exchange in May.

Polymarket's revenue is being fueled by growth in that U.S. exchange, which operates as a separate trading venue from its decentralized finance international platform. The domestic exchange saw more than $14.5 billion in notional volume in October, up from $4 billion in June, according to data analytics platform TickerTracker.

That increase has been driven by a series of highly traded events, including the FIFA World Cup over the summer and the start of the NFL season in September. Volume has been supported by the growing popularity of Combo event contracts, which work similarly to sportsbooks' multi-leg parlays, accounted for more than 70% of volume traded on the platform on Sunday.

The revenue growth since June also comes after the company began a fresh $1 billion funding round that values Polymarket at $21 billion.

Polymarket still faces near-term headwinds, though. The Commodity Futures Trading Commission is conducting a broad investigation into the company, with questions surrounding advertising practices and whether the company in the past violated a settlement with the agency to bar U.S. residents from accessing its international exchange.

The company also may face increased scrutiny from a Democratic congress, partially due to the position of President Donald Trump's son — Donald Trump Jr. — as an advisor to the company.

But Polymarket previously told CNBC it would work with lawmakers as they begin to understand the growing prediction market industry. "We welcome scrutiny," a spokesperson said.

Disclosure: CNBC and Kalshi have a commercial relationship that includes customer acquisition and a minority investment.