How to compare two contracts on the same question
Two venues can quote the same headline and still be selling different contracts. Check the wording, the source, and the deadline before you compare the numbers.
By Sloppy Stakes EditorialPublished 7 min read
What you'll be able to do
- Run a structured comparison across subject, predicate, threshold, deadline, time zone, unit, authority, cancellation, outcome completeness and payoff condition.
- Decide whether a pair is an exact match, merely similar, or in conflict.
Before you start
- A working understanding of resolution authorities.
What this guide won't do
- A comparison is a judgement about wording, not a prediction about settlement.
Two contracts are comparable only when they pay out on the same event under the same rules, and a matching headline is not evidence that they do. Before you set two numbers side by side, confirm the wording, the resolution source, the deadline, and the payout: if any one of those differs, the gap between the prices is telling you about the contracts, not about the world.
Fact: platform documentation directs readers to each market's written rules and named resolution source rather than to the market title, which is why two similarly titled markets can settle differently.
This guide assumes you already know what a contract is and which price your screen is showing. If either is shaky, start with what a prediction market is, then how to read a market price; settlement mechanics live in the guide on how markets resolve.
Check these in order
Predicate. What exact action, threshold, or state must occur? Announced, enacted, certified, and reported are four different predicates even under one headline.
Subject and scope. Same person, office, jurisdiction, and entity? A national figure and an agency-specific figure are different contracts.
Resolution source. Which named source decides, and is it the same named source on both venues? If one names a specific official release and the other names an aggregator or leaves discretion, they are not the same contract.
Deadline and time zone. Compare deadlines as absolute instants, not as calendar words; an unqualified by Friday is ambiguous until you know the zone and offset, which is exactly what a timestamp standard exists to remove.
Fact: RFC 3339 defines an internet timestamp format that fixes date, time, and UTC offset, so two deadlines can only be compared reliably once each is expressed with an explicit offset.
Observation window. Does the event have to happen within a window, or merely be true at a single measurement moment?
Payout structure. A binary YES/NO payout and a scalar or bracketed payout are not interchangeable, even when the question sounds identical.
Ambiguity and void rules. What happens if the source is silent, revised, or delayed? A contract that voids and a contract that resolves NO behave very differently in exactly the cases that matter.
Which price you are quoting. Last trade, mid, and the best executable bid or offer are different numbers, so comparing a last trade on one venue with a mid on another compares measurement conventions as much as beliefs.
Fact: platform pricing documentation describes prices as arising from resting orders in an order book rather than from a single published estimate, so the quoted number depends on which part of the book is reported.
Costs and frictions. Fees, settlement currency, funding, and withdrawal terms differ by venue; whether they are large enough to explain any particular gap is UNKNOWN here, because this guide states no venue fee figures.
Access and eligibility. If you cannot actually trade both contracts, the comparison is analytical, not actionable.
Price proximity is not equivalence
Two contracts trading at nearly the same price may still settle on opposite outcomes, and two trading far apart may be describing the same world under different rules. Equivalence is established by matching terms and payoff semantics plus review evidence, never by a small numeric gap. Where the terms differ or you have not read them, the honest label is UNKNOWN rather than a difference you have explained.
What would change this guide
Venue rulebooks change, and one rulebook page behind this checklist could not be retrieved on 14 August 2026, so nothing here should be read as a current statement of any specific venue's rules. Read the live rules for the two contracts in front of you; this page is a procedure, not a substitute for them, and it is not advice about whether to take a position.
How AI was used here
AI re-retrieved the cited sources, restructured the comparison checklist, and drafted the prose. It did not verify venue-specific contract terms and did not perform human editorial review.
Sources
- Resolution primaryPolymarket · Official description of market rules, resolution sources, end dates, and edge cases.
- Market Rules primaryKalshi · Official guide to reading market rules and understanding settlement criteria.
- How are prices determined? primaryKalshi · Official educational documentation on order-driven YES/NO pricing and probability interpretation.
- RFC 3339: Date and Time on the Internet: Timestamps primaryInternet Engineering Task Force · Internet standard profile used here as the recommended portable timestamp representation.
Read next
- What Is a Prediction Market?
A prediction market is a market in contracts that pay a fixed amount if a defined event happens. The price is what people will pay for that payoff right now — useful as a probability estimate, but not a fact about the world.
- Bid, Ask, Spread, Depth, and the Price You Can Actually Trade
Last trade, midpoint, bid, and ask are different numbers, and the one a venue displays is a formatting choice. The price you can actually get also depends on how much depth exists for the size you need.
- How YES and NO Contracts Resolve
YES and NO settle from written contract terms: the condition, deadline, time zone, resolution source, and the rules for messy edge cases.