Polymarket Combos: How Polymarket Parlays Actually Work

A Polymarket Combo is one multi-leg YES/NO position built from several underlying prediction-market outcomes. Every selected leg must finish the right way for the Combo to pay. One wrong leg loses the Combo.

People also search for this as a Polymarket parlay. Same intent, one canonical page. We are not making a second article wear a fake mustache.

Affiliate disclosure: Business Dog may earn money if you open or use Polymarket through a qualifying link here. That does not change the math, the verdict, or the price you see. Yes, this link can make us money.

What happens when you build a Polymarket Combo?¶

You choose multiple prediction-market outcomes as legs. The system derives complementary YES and NO positions for that exact combination. That combination becomes one tradeable object.

If the Combo is “A and B and C,” its YES position wins only when A, B, and C all resolve in the selected direction. The position does not pay two-thirds because two legs were right. There is no participation trophy in conjunction logic.

Official Polymarket documentation describes each Combo as a pair of derived position IDs. Those IDs complement the ordinary CLOB token IDs: an underlying outcome can trade by itself on the order book or serve as a leg inside a Combo.

Why is 90% + 90% + 90% only 72.9%?¶

Because “all three happen” requires multiplication under independence:

0.90 × 0.90 × 0.90 = 0.729

So the probability all three win is 72.9%. The chance at least one fails is:

1 − 0.729 = 0.271 = 27.1%

A 90% leg feels safe. Three 90% legs feel like three safe things. Unfortunately, multiplication does not care about the vibe.

This benchmark is exact only if the legs are independent. If one result changes the chance of another, multiplying the displayed probabilities can misstate the package probability.

How does Polymarket price a Combo through RFQ?¶

Combos use a request for quote, or RFQ, rather than asking the ordinary single-market order book to invent a package price.

The current official flow is unusually specific:

1. A user creates an unsigned Combo request.
2. Connected market makers receive it.
3. They have a 400 millisecond submission window to compete with signed executable quotes.
4. The best quote returns to the user.
5. The user has a 10-second acceptance window to sign.
6. If “last look” is enabled, the selected market maker has one second to confirm or decline.
7. A confirmed quote executes and position updates follow.

The RFQ is why a Combo quote can differ from multiplying the current displayed leg prices. The quote packages liquidity, timing, correlation, size, and market-maker risk into one executable number.

It is also why Business Dog does not show “live Combo prices.” In Phase 0, the official public API exposed the catalog of markets that may be used as legs, while public requester quote integration was still marked “Coming Soon.” Maker quote endpoints require authenticated market-maker access. Our calculator accepts a quote you enter; it does not forge one out of single-leg prices.

Can you cash out a Polymarket Combo?¶

Yes, official help documentation says a Combo can be sold before resolution. Cashing out means another participant buys the Combo shares at the current available price. You are not redeeming early for the original projected payout.

That distinction explains nearly every frustrating cash-out screen:

• Your position can be valid and still have no buyer right now.
• A buyer can exist for a smaller size but not the full position.
• The quote can move while you submit.
• Guardrails can block a trade when price movement or shallow liquidity would create excessive slippage.
• The cash-out price can be below what the position appears “worth” from leg midpoints.

Why can't you cash out a Polymarket Combo?¶

Work through this list in order:

1. 1

   Check whether the Cash Out button is inactive

   Polymarket says an inactive cash-out button occurs when no counterparty is offering a quote for that specific position. Waiting for a buyer or market maker is sometimes the only honest fix.

2. 2

   Try a smaller size

   A smaller position is easier for available liquidity to absorb. Reducing size can turn an unfillable request into a quote, though it does not guarantee one.

3. 3

   Refresh and request a current price

   If underlying markets moved, an older interface state may no longer be usable. Refresh the page and review the current quote rather than repeatedly submitting yesterday's idea of today's price.

4. 4

   Check market status and product availability

   The Help Center described Combos as available on supported sports moneyline, spread, and total markets at the verification date. Supported markets can change. A market starting, pausing, resolving, or falling outside the supported set can change what actions are available.

5. 5

   Use official support when the state looks wrong

   If the button and position state contradict current product guidance, contact Polymarket through the in-product chat or official support address. Include the position and error details; do not post private keys or seed phrases to anyone.

Why is the Polymarket Combo button greyed out?¶

For building or cashing out, grey usually means the platform cannot obtain an executable quote at that moment. Official troubleshooting suggests removing a leg, reducing the amount, or waiting for a willing market maker. On cash-out, it specifically points to the absence of a quote for your position.

Do not interpret grey as “the position is secretly worthless” or “Polymarket stole the button.” It is interface language for unavailable execution, and unavailable execution can have several market-state causes.

How should you compare a Combo quote with the leg math?¶

1. Convert each leg's relevant executable price into a probability.
2. Multiply only as an independence benchmark.
3. Convert the Combo quote into its own implied probability.
4. Report the difference in percentage points.
5. Investigate correlation, liquidity, size, and market timing before assigning a cause.

Example: three 90% legs create a 72.9% independent benchmark. If a manually entered Combo quote is 76¢, the quote is 3.1 probability points above that benchmark. That sentence is factual. “The market maker charged 3.1%” is not established. “I found 3.1% edge” is also not established.

The Polymarket fees explainer covers the ordinary Predictions fee formula. Do not force that formula onto an RFQ difference that may come from other mechanics.

If the cents-to-probability step is still slippery, the Polymarket probability calculator shows the single-position math before several legs start multiplying the anxiety.

What is the public Combo API good for today?¶

The unauthenticated GET /v1/rfq/combo-markets endpoint returns active markets that can serve as legs, ordered by volume, with position IDs, outcome prices, tags, and cursor pagination. That is useful for discovery and future research design.

It is not a public executable quote endpoint. Collecting quote dispersion would require legitimate requester access, a defined methodology, storage, product-terms review, and enough observations to say something beyond “we found a database and became emotional.” None of that is claimed here.

The Combo is one position, the RFQ is one moment, and the “safe” legs multiply into something less safe than the sales pitch in your head. Our intern CowDog tested the multiplication. He is now seeking therapy.

Sources

1. Polymarket — How Combos Work
2. Polymarket API — Get Combo Markets
3. Polymarket Help Center — What are Combos?
4. Polymarket — Collateral Return