How a venue changes its rules, and where you can see it coming

The question usually arrives after the fact: a fee that is higher than it was last month, a contract whose source changed, a feature that now only lets you close. Could they do that, and could you have known? The answer depends less on the venue than on who wrote the rule in question. An exchange's rule goes through a federal procedure with a clock. A broker's fee is a line in the broker's own schedule. An offshore venue's terms are a page the venue edits.

This page reads the procedure for the first, two sections of the CFTC's Part 40 and Kalshi's rulebook, version 1.29, with two of Kalshi's own fee filings as worked examples; then one broker's fee schedule; then one offshore venue's terms. How a new contract gets listed in the first place, and what self-certification means for the legal fight over event contracts, is on event contract or swap; this page is about what happens after.

How it works

On a US exchange: file, post, wait ten business days

A designated contract market changes a rule by certifying it. Under 17 CFR 40.6(a), before implementing any rule the Commission has not approved, the exchange files the rule with a certification that it complies with the Act, and the submission must meet three conditions a reader can use:

• the exchange certifies that it "posted a notice of pending certification with the Commission and a copy of the submission, concurrent with the filing ... on the registered entity's website";
• "The Commission has received the submission not later than the open of business on the business day that is 10 business days prior to the registered entity's implementation of the rule or rule amendment";
• the filing includes "the date of intended implementation" and a brief explanation of any substantive opposing views.

The Commission then has those 10 business days to review it. If it issues a stay, because the rule "presents novel or complex issues", is inadequately explained or may be inconsistent with the Act, it gets "an additional 90 days", within which it must open a 30-day public comment period. Without an objection or a withdrawal of the stay, the rule takes effect at the end of the 90 days.

A fee filing in Kalshi's public notices folder shows the clock in use. Dated 19 October 2026, for its perpetual futures, it says Kalshi "is implementing on or after October 30, 2026, ten (10) business days after the self-certification date of this filing".

Kalshi's rulebook adds its own publication duty. Rule 2.17(c) says it will publish on its website "a Notice with respect to each addition to, modification of, or clarification of, the Rules, the Matching Engine, and any Company Contract Specification prior to the earlier of" the effective date and the filing with the Commission. Rule 2.17(e) treats a notice as given to a broker's customers once it is sent to the broker. And Rule 3.6(d) puts the reading on you: each participant "is required to review the 'Notices' section of the Kalshi website".

New contracts: one business day

Listing a new contract runs on a shorter clock. Under 17 CFR 40.2(a), the Commission must have received the certification "by the open of business on the business day preceding the product's listing", with a copy posted on the exchange's website at the same time. A series that did not exist on Monday can trade on Tuesday. That is a new product beside yours, not a change to the one you hold.

Fees under a dollar a contract: the regulation asks for nothing

Part 40 sorts some changes into lighter procedures, and fees are one of them. Under 40.6(e), an exchange may put a rule into effect "without certification or notice to the Commission" if it "maintains documentation regarding all changes to rules" and the rule governs, among other things:

Fees or fee changes, other than fees or fee changes associated with market making or trading incentive programs, that: (A) Are less than $1.00 per contract; or (B) Relate to matters such as dues, badges, telecommunication services, booth space, real time quotations, historical information, publications, software licenses or other matters that are administrative in nature.

A fee of a dollar or more a contract that a third party sets, or that is unrelated to trading, clearing, delivery or dispute resolution, goes on a weekly summary notice under 40.6(d) instead.

Kalshi's trading fee sits far below the line. The schedule it filed in 2022 charged round up(0.07 x C x P x (1-P)), where P is the price and C the number of contracts, and its own table puts that at 2 cents for one contract at 50 cents; because P x (1-P) is never more than a quarter, the formula cannot reach a dollar a contract at any price. The current schedule is on the Kalshi card. So the federal procedure, read on its own, does not require an exchange to file or announce a change to a fee of that size before it takes effect, unless the fee belongs to a market-making or trading-incentive programme.

Kalshi's rulebook goes further than the regulation. Rule 3.13(b) says fees may be charged "in such amounts as may be revised from time to time to be reflected on the Company's Website", and Rule 3.13(e) adds a commitment of the exchange's own: "If Kalshi determines in the future to impose dues or additional fees, the Participants will be provided notice of the change at the time the amended fees are filed with the Commission. The new fee structure will be implemented no earlier than on the first available trade date for which the change may be implemented according to the Commission's self-certification filing requirements as set forth in CFTC Regulation 40.6(a)." The rule speaks of dues or additional fees; read it for yourself to judge how far it reaches a change to an existing formula.

The 2022 filing shows the exchange using the full procedure for a fee change of cents. Dated 9 September 2022 and filed "Pursuant to Commission Regulation 40.6(a)", it cut the fee on Kalshi's index markets from 0.07 to 0.035 in the same formula, took effect on 22 September 2022, and quoted the same commitment, then numbered Rule 3.6(e). A reader can count on the rule as written; the regulation alone would not have required the filing.

Contract terms mid-life: powers already in the rulebook

Some changes need no new rule, because the rulebook already grants the power. Kalshi's Rule 7.2(a) lets the exchange, if something affects "the reliability or transparency of a Contract's Source Agency or the Underlying", designate a new source agency and underlying "and to change any associated contract specifications after the first day of trading", and announce the decision on its website. Rule 7.2(b) and (c) let it move an expiration date later for a rescheduled event or delayed data, or earlier when the outcome occurs early. The change of source agency on Kalshi's temperature contracts is worked through on what a temperature market settles on.

Emergencies run the clock backwards. Under 40.6(a)(6) an emergency rule is filed before it takes effect if practicable, and otherwise "at the earliest possible time after implementation, but in no event more than twenty-four hours after implementation". Kalshi's Rule 2.8 lets its board or at least two members of management, with the chief executive's approval, adopt a temporary emergency rule "without giving prior notice to, or securing prior approval from the Commission". Its definition of an emergency includes manipulation, system failures, and "Any action taken by the United States, any foreign government, any state or local governmental body" that may directly affect trading. Its list of reasonable responses includes modifying position limits, cancelling a contract and returning the funds paid, shortening or extending expiration, suspending trading, and "Changing a Contract's terms and conditions and/or specifications". The rule says plainly that the chance of an emergency "is one of the risks that Participants should consider".

On a broker: two fees, two schedules

A broker in front of an exchange charges its own fee on its own schedule, and passes the exchange's fee through. Public's fee schedule, last updated on 13 October 2026, shows both lines for event contracts: a transaction fee of 0.01 dollar per contract from Open to the Public Investing, a CFTC-registered futures commission merchant, and an exchange fee of 0.01 dollar per contract, "charged by the exchange and passed on to the customer".

On how either may change, the schedule is direct. Its footnote says the event-contract exchange fees "are set by KalshiEx LLC and are subject to change without notice". For its own fees: "Public Investing reserves the right to waive or vary its fees, permanently or for a period of time, at its sole discretion for any reason. Fees are subject to change at any time." The Part 40 procedures above are written for the exchange that files them; the broker's line on your statement carries the broker's terms, and this one promises no notice period.

Offshore: effective upon posting

An offshore venue's terms are a contract with the operator, changed by the operator. Predict.fun's Terms of Service, last updated on 18 November 2025, put it in section 3: "We reserve the right, in our sole discretion, to modify the Terms at any time or from time to time. The modified Terms will be posted on the Site and any other Interface and will provide the last updated date at the top. Any modified Terms will become effective upon posting." The same section reserves the right to modify, suspend or disable the site or its features "with or without prior notice to you, ... for any reason whatsoever, including, without limitation, to only allow open contracts to be closed".

On such a venue some rules are also code, and code has administrators. What an admin role can do to a price market and to the collateral is on what a crypto price contract settles on and what backs the dollar on an on-chain venue.

What you can do about it

Read the exchange's notices, not the app's banner. On a US exchange every certified change is posted on the exchange's website when it is filed, and Kalshi's rulebook makes reading that section your job. A filing dated today shows you the earliest day the change can take effect: ten business days on, unless the Commission stays it.

Do not assume ten days for a fee. The regulation leaves a fee change under a dollar a contract outside both certification and notice. Find the rule in the exchange's own rulebook that says what it promises instead; on Kalshi that is Rule 3.13(e), and its wording is the whole of the promise.

On a broker, check two schedules. The broker's own fee and the exchange fee it passes through change separately. Public's schedule tells its customers to "always check the current posted Fee Schedule before placing trades"; on a schedule that promises no notice, that is the only check there is.

On an offshore venue, keep the date. The last-updated date at the top of the terms is the only signal the terms promise. Note it when you deposit and look again before you add to a position.

Treat emergency powers as part of the contract. The rulebook lists what an exchange may do in an emergency, changing a contract's terms included, and defines emergencies to include actions by governments and courts. That list is published, and it is the honest upper bound on what can change without warning. It is not a prediction that any of it will be used.

Know who decides the outcome as well as the rules. A change to the source a contract settles on is a change to who decides; who decides the outcome covers that side, and the prediction market venues listing records each venue's regulator and terms.