GUIDE · How to Read a Market's Rulebook Before You Trade
How to Read a Market's Rulebook Before You Trade
The most expensive sentence in prediction markets is "I did not read the rules". It is also the most common one in settlement disputes. The documented cases are not exotic: a market on a leader's death that settled at a fraction of what holders expected because of a carveout, a market that paid out on data about to be deleted, disputes described by a state attorney general as decided by the platform itself. Every one of those was visible in the rulebook before the trade.
This page is a carveout-hunting checklist. Read the rulebook against it before you enter, and the settlement surprises mostly stop happening.
Why the Rulebook Is the Trade
A prediction market contract is not the event. It is a legal instrument that pays based on a defined question, resolved by a defined source, on a defined timeline. The gap between the event and the contract is where the money goes. The rulebook is the only document that defines that gap.
The clearest documented example is the market on the Iranian leader's death. The question, read plainly, is about a death. The contract, read carefully, contained a carveout under which the market settled at a partial value, around 39.5% instead of the $1.00 a straightforward reading implies. Traders who held YES near $1.00 discovered the carveout after the event resolved, and the discovery was expensive.
Nobody who read the rulebook before trading needed to discover it then. That is the entire argument for this checklist.
The Checklist: Seven Things to Hunt For
1. The Resolution Source
Who or what decides the outcome? The rulebook should name a source: an oracle, an API, a committee, a government announcement, or the platform's own judgment. The strength of that source determines the strength of the market. A market that resolves on a single unverifiable source is a market whose payout you cannot predict.
Red flag: "Determined by the platform" or no named source at all. The Massachusetts Attorney General's complaint about Kalshi states the platform "writes the rules for the contract, determines the basis for settlement", with no independent intermediary. Where the platform is the judge of its own rules, the rulebook is the only protection you have, so read it twice.
2. The Exact Event Definition
What precisely counts as the event happening? Not "the leader dies" but "the leader dies by date, per the named source, with the named exceptions". Definitions hide the most value. A market on "X wins the election" can mean the electoral college, the popular vote, the AP call, or a concession, and each resolves differently.
Red flag: An event definition that does not name the source of the outcome. If you cannot say exactly what information triggers a YES payout, you are trading a guess.
3. Carveouts and Special Conditions
This is the section that made the Khamenei market famous. Carveouts are conditions under which the market settles differently from the plain reading: partial settlement, a defined fallback value, or a specific source override. They are usually buried in the middle of the rule text, and they are the most likely part of the rules to change the payout.
Red flag: Any clause that starts with "notwithstanding", "in the event of", or "if the resolution source is unable to determine". Read it out loud and check what it does to your position at each plausible outcome.
4. The Effective Date and the Deadline
When does the event window close, and when does the market settle? A market can stay open after the event it tracks has effectively resolved, which the Massachusetts complaint documents as a real failure mode. The rulebook should give you both dates. If the settlement date can drift, the drift is a risk you are carrying.
Red flag: An event deadline that differs from the settlement date without explanation. Time is part of the price.
5. Void and Cancellation Conditions
Under what conditions does the market void instead of settle? A void usually returns the cost basis, which protects you, but the conditions matter: some voids pay nothing, and some are decided on timelines that favor one side. Know the difference between a void that returns your money and a dispute that decides how much of it you keep.
Red flag: A void condition defined by the platform's judgment rather than by an objective trigger.
6. The Settlement Timeline
How long after the event does the market settle? The Spotify case is the warning here: the market paid out minutes before Spotify deleted 523,000 fraudulent streams. The payout used the data as it existed at settlement time, and the correction came too late. A slow settlement window is protection against exactly that failure; a fast one is exposure to it.
Red flag: A settlement window shorter than the time it takes the underlying data to be verified.
7. The Dispute Path
What happens if you disagree with the settlement? The honest answer on both major platforms is: very little. There is no independent appeals body, and the documented record shows complaints going unanswered at a high rate. The rulebook may not even mention disputes. If it does not, assume there is no path, and size the position so a disputed settlement is survivable.
Red flag: A rulebook with no dispute section. The absence is the answer.
How This Checklist Changes Your Trades
Run the checklist before entry and three things change:
- The price changes. A market with a carveout risk is worth less than its raw probability implies. You can price the haircut in our arbitrage calculator before you enter.
- The position changes. If a disputed settlement would hurt, size down. Our Risk Management: The 5-Rule Framework covers sizing for exactly this kind of tail risk.
- The market selection changes. Two markets on the same event with different rulebooks are different trades. The one with the named source, the objective trigger, and the slower settlement window is the better risk, all else equal.
For the full picture of what happens when settlement goes wrong, see our guide on how event contracts settle and what happens when you disagree.
FAQ
Q: Where do I find the rulebook on Polymarket?
A: Open the market and read the rules section before placing an order. If the rules are not visible on the market page, treat that as a warning sign and do not trade the market.
Q: Where do I find the rulebook on Kalshi?
A: The contract details page includes the rulebook for each market. Read it before entry, and note the resolution source and the settlement timeline specifically.
Q: What is a death carveout?
A: A condition in a market's rules that changes the payout when the event happens in a defined way. The Khamenei market settled around 39.5% instead of $1.00 under its carveout, which holders discovered after the event.
Q: What is the single most important thing to check?
A: The resolution source. If you cannot name who or what decides the outcome, you cannot price the trade. Everything else in the checklist is detail on top of that.
Q: Can the rules change after I buy?
A: The rules should not change after entry, but the settlement source can be applied in ways the plain reading does not predict. The documented carveout cases are exactly this. Read the full rule text, not the question headline.
Q: What if I disagree with a settlement?
A: The documented recourse is thin: platform support, BBB, and regulators, with no independent appeals body on either platform. The checklist exists so you never need to find out.
Last updated: 2026-08-11