The regulated US exchange of Polymarket has officially launched multi-leg combo trades in a beta test, marking a significant milestone following the previous offering through an RFQ pricing system during the FIFA World Cup.
Both versions of the product utilize a request-for-quote mechanism for pricing instead of Polymarket’s standard central limit order book.
Traders can submit a request to combine multiple outcomes into a single position, with market makers having 400 milliseconds to provide a price quote.
Once an offer is accepted, traders have five seconds to confirm the transaction. Market makers can opt for a “Last Look” feature, giving them an additional one-second window to decide on the trade fill after a trader accepts the quote.
For the combo position to pay out, each leg must settle in the trader’s favor; any incorrect outcome will void the entire ticket. Since the pricing is based on the visible order book, users typically can only take the “yes” side of a combo unless they access the market via the API, leading to casual bettors losing out due to their overwhelming support for the “yes” side.
From debut to beta launch
The offshore platform, which restricts US IP addresses, introduced combo trading on June 10, covering moneyline, spread, and total markets.
Polymarket confirmed the sports-only release on X, noting that “combos are now live.” As of now, no specific timeline has been set for expanding the product to political contests, breaking news markets, or other event categories on either platform.
The regulated US exchange successfully self-certified the product with the Commodity Futures Trading Commission (CFTC) in May under the name “Combinatorial Athletic Outcome Contracts” (CAOCs) and completed its first trade on August 5 after around 10 weeks of processing.
The product is currently in the beta phase with the option to create combos not yet visible on the Polymarket US app. The desktop site has not officially launched, and all activities to date have been part of the testing environment. Beta users are restricted to combos with up to 10 legs.
Following the debut on August 5, combo trading on Polymarket US has reached $7.4M in volume, with taker-side stakes totaling $928,093 across 16,173 trades — a significant increase since last Thursday.
Polymarket has also introduced a public API endpoint for combo market data that does not require authentication tied to the central limit order book. This allows external trading dashboards and analytics services to retrieve combo pricing independently.
Fees, settlement, and liquidity considerations
Polymarket has not finalized the fee structure for multi-leg combos, or the settlement process when one leg resolves before others.
Given fewer market makers pricing combos compared to single-outcome markets, the company acknowledges that thin liquidity and wider bid-offer spreads may be observed in the product.
Continued Growth in Kalshi’s Parlay Business
While Polymarket US refined its product for beta launch, Kalshi’s parlay volume surged from $4.77B in May to $13.78B in July, with August volume projected to follow a similar trajectory despite a lighter sports schedule.
Kalshi generated $25M in parlay taker fees within the first 16 days of August alone. The parlay product currently supports combos with more than 30 legs, surpassing Polymarket’s beta cap of 10 legs.
Kalshi is preparing to implement maker fees on parlay bets, a segment previously exempt from fees where market makers could trade without charge and even qualify for liquidity incentives.
The introduction of fees will align with Kalshi’s fee schedule for other contract types, where maker fees are set at approximately a quarter of taker fees and are adjusted based on odds — higher fees for near-even money outcomes and lower fees for extreme odds. Despite introducing fees, parlay fees remain relatively low as a share of volume compared to other contract types, indicating that parlay bets contribute significantly to Kalshi’s fee revenue.
The competitive exploration into multi-leg sports wagers by both platforms coincides with an investigation into product origination. Polymarket is reviewing potential imitation by Kalshi, compiling an internal document with approximately 12 instances where Kalshi allegedly released similar products shortly after Polymarket’s launches, spanning sports, weather, and international conflict contracts.
In a phone interview with The Post, Polymarket’s head of marketing, Matthew Modabber confirmed the internal review, stating, “Certain patterns have raised concerns about potential imitation.”
Shayne Coplan, representing Polymarket, went a step further by accusing the rival platform of deliberate imitation, saying, “There is clear intent behind their imitation. They are closely following our developments.”