If you have ever placed a parlay at a sportsbook, a Polymarket Combo will look instantly familiar. You pick several outcomes, tie them into one bet, and win only if every pick lands. The payout climbs with each leg you add. Same shape, same appeal.
Look closer, though, and a Combo behaves differently from a parlay in two structural ways that matter. It stays tradable until it resolves, so you are not locked in the moment you place it. And its price is set by competing market makers bidding for your order, not by an operator deciding the margin. Those two differences are the whole story, and they are what this explainer is about.
What a Combo actually is
In Polymarket's own words, Combos are "multi-leg positions that combine multiple underlying market outcomes into one YES or NO position." You bundle several individual market picks into a single trade, and, as the help documentation puts it, "you only win if every leg of your Combo resolves in your favor." One leg missing means the whole Combo loses. That all-or-nothing structure is exactly what a parlay does.
The feature is narrow for now. Polymarket states that Combos are "currently available on sports markets only," built from three familiar bet types: moneyline, spread, and total. No expansion beyond sports has been announced, so anything you read about non-sports Combos should be treated as speculation until Polymarket says otherwise.
Difference one: a Combo stays tradable
A sportsbook parlay is a locked ticket. Once you place it, you hold it to the end. If the first leg wins and the second is looking shaky, there is usually nothing to do but wait.
A Combo is different because it is a position, not a ticket. Polymarket's documentation is explicit: "You can sell your Combo before resolution," and "if the odds shift, you can sell your Combo shares at the current market price." You are not locked in. If two of your three legs have landed and the third is still live, you can sell the position and take its current value rather than risk everything on the last leg. You can also cut a losing Combo early instead of holding a near-certain loss down to zero.
This is the single biggest behavioural difference from a parlay, and it follows directly from the fact that a Combo is a tradable instrument that exists right up until the underlying markets resolve.
Difference two: the price comes from competing market makers
The second difference is about who sets the price. At a sportsbook, the operator prices the parlay and builds in its margin. You take that price or leave it.
A Combo is priced through a request-for-quote, or RFQ, auction. According to Polymarket's market-maker documentation, building a Combo creates a request that "starts an auction among connected market makers." Those market makers compete to fill the order, each submitting a signed quote. The timings are specific: market makers have up to 400 milliseconds to submit their quotes, the system returns the best quote to you, and you then have up to 10 seconds to accept it by signing the trade.
The practical effect is that your Combo's price is the best bid from a set of competing professionals, generated fresh for each request, rather than a number an operator has set with a built-in hold. If no market maker is willing to fill the order, the accept button is simply greyed out, so a Combo only exists when someone is prepared to price it.
How the price and payout are calculated
The maths behind a Combo is the maths of combined probabilities. Polymarket states that "the payout on a Combo is calculated by multiplying the implied probabilities of each leg together." Combine three legs each trading at an implied 50 percent and the Combo reflects the combined 12.5 percent chance of all three landing, with the payout scaling to match. More legs, or longer-odds legs, mean a lower combined probability and a larger potential payout, which is the same risk and reward trade a parlay offers.
Prices are quoted in pUSD, Polymarket's unit of account, as a price per YES Combo share. A quote of 0.45 means 0.45 pUSD per share. That number moves as the underlying markets move, which is what makes selling before resolution possible in the first place.
Why the quoted price and the multiplied odds can differ
The two things Polymarket describes, the multiplied implied probabilities and the RFQ quote, are not the same number, and the difference is where the interesting part of a Combo lives.
Multiplying the implied probabilities of each leg gives you what the Combo would be worth if the legs were independent, meaning the outcome of one told you nothing about the others. That is the textbook baseline. But Combos are sports only, and sports legs are frequently correlated. A moneyline and a total on the same match tend to move together: a blowout makes the favourite's win and the over more likely at once, while a low-scoring grind pulls both the other way. Two legs on the same game are rarely independent.
A market maker quoting a real price has to account for that correlation, and the naive product of the implied probabilities does not. So the RFQ quote you are offered can sit above or below the multiplied baseline depending on how the legs are related. Where correlated outcomes reinforce each other, the true combined probability is higher than the product suggests, and where they offset, it is lower.
Polymarket's documentation does not say how market makers model this, and this is not a claim that they use any particular method. The point is structural. The platform describes the payout as the product of implied probabilities and the price as the output of a competitive RFQ auction, and those two mechanisms only agree when the legs are independent. For a sports-only product where they often are not, the gap between the multiplied baseline and the quote you actually get is, in effect, the market makers' collective view of how the legs move together.
Where a Combo sits among prediction-market structures
It helps to place a Combo next to two things it resembles but is not.
A sportsbook parlay is the closest cousin: all legs must hit, and the payout multiplies. The difference, as above, is that a Combo is tradable and competitively priced.
A conditional market is the other neighbour, and it is worth distinguishing carefully. As our explainer on Polymarket's conditional markets sets out, a conditional contract only settles if a specified antecedent event happens first, and if that antecedent fails, the conditional contract voids and stakes are returned. A Combo does the opposite. If one of its legs fails, the Combo does not void and refund; it simply loses. Nothing is conditional, and nothing is returned. Every leg has to resolve YES for the position to pay.
So a Combo is a third structure. Like a parlay, it is all-or-nothing across every leg. Unlike a parlay, it stays tradable to resolution and is priced by an RFQ auction. And unlike a conditional market, a failed leg does not void the position, it settles it as a loss.
Which Polymarket runs Combos, and the UK position
A note on where this lives. Polymarket operates as two separate entities. Its own disclaimer states that "Polymarket US is operated by QCX LLC d/b/a Polymarket US, a CFTC-regulated Designated Contract Market," while the international platform "is not regulated by the CFTC and operates independently." The Combos documentation and product pages described here sit on that international platform, which settles positions on-chain in pUSD. Polymarket has published nothing stating that Combos are offered on the CFTC-regulated US venue, so we make no claim either way about US availability.
For UK readers, the access position for Combos is the same as for the rest of Polymarket's international platform, which does not serve UK customers. Our pieces on whether prediction markets are legal in the UK and the honest answer on using Polymarket from the UK cover that position in full, and our guide to legal alternatives to Polymarket for UK users points to the venues that operate inside the UK Gambling Commission's licensed perimeter.
iPredicta covers the discovery and analysis side of prediction markets. We track contracts and prices across the global landscape, including Polymarket, and explain how newer structures like Combos actually work, so readers can understand what they are looking at. We do not operate a betting product, and nothing here is trading advice.
Frequently asked questions
What is a Polymarket Combo?
A Combo is a multi-leg position that bundles several sports market outcomes into a single YES or NO trade on Polymarket. In Polymarket's words, Combos are "multi-leg positions that combine multiple underlying market outcomes into one YES or NO position," and you win only if every leg resolves in your favour. It is Polymarket's equivalent of a sportsbook parlay, with two structural differences: it stays tradable until it resolves, and its price is set by competing market makers rather than by an operator.
How is a Combo different from a sportsbook parlay?
Two ways. First, a parlay is a locked ticket, whereas a Combo can be sold before resolution at the current market price, so you are not committed to holding it to the end. Second, a sportsbook sets the parlay price and its own margin, whereas a Combo is priced by a request-for-quote auction in which market makers compete to fill your order. The all-or-nothing "every leg must hit" structure is the same in both.
Can you sell a Combo before it resolves?
Yes. Polymarket's documentation states that "you can sell your Combo before resolution" and that "if the odds shift, you can sell your Combo shares at the current market price." That is the main behavioural difference from a parlay, which cannot usually be exited once placed.
How is a Combo's payout calculated?
Polymarket states that "the payout on a Combo is calculated by multiplying the implied probabilities of each leg together." Three legs each at an implied 50 percent give a combined 12.5 percent chance, and the potential payout scales with that combined probability. Prices are quoted in pUSD per YES Combo share.
Are Polymarket Combos available in the UK or on Polymarket US?
The documented Combos feature sits on Polymarket's international platform, which does not serve UK customers, so the UK access position is the same as for the rest of that platform. Polymarket describes its US arm as a separate, CFTC-regulated Designated Contract Market operated by QCX LLC, and it has not published anything stating whether Combos are available there, so we make no claim about US availability. UK readers can see our explainers on prediction-market legality in the UK and the licensed alternatives for the fuller picture.
What markets can you build a Combo from?
At present, sports only. Polymarket says Combos are "currently available on sports markets only," using moneyline, spread, and total bet types across its listed games. No non-sports expansion has been announced.