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

A US exchange's rule changes wait ten business days in public; a fee under a dollar a contract need not. Broker fees and offshore terms change when posted.

*https://predictionmarkets.tools/guides/how-a-venue-changes-its-rules · background to Prediction Market Venues*

**Answer:** It depends on who wrote the rule. A US exchange must certify a rule change to the CFTC and post it on its website at least 10 business days before it takes effect, but a fee change under 1.00 dollar per contract, where Kalshi's trading fee sits, needs neither certification nor notice under the regulation; Kalshi's rulebook promises notice anyway. A broker's own fees, and an offshore venue's terms, change when the firm posts them.

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](https://predictionmarkets.tools/guides/event-contract-vs-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](https://predictionmarkets.tools/tools/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](https://predictionmarkets.tools/guides/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](https://predictionmarkets.tools/guides/what-a-crypto-price-contract-settles-on) and [what backs the dollar on an on-chain
venue](https://predictionmarkets.tools/guides/what-backs-an-on-chain-venues-dollar).

## 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](https://predictionmarkets.tools/guides/who-decides-the-outcome) covers that
side, and the [prediction market venues](https://predictionmarkets.tools/categories/prediction-market-venues) listing records each
venue's regulator and terms.

## Tools this bears on

- [Kalshi](https://predictionmarkets.tools/tools/kalshi.md) — A CFTC-designated exchange for event contracts, settled in dollars against named sources.
- [Polymarket US](https://predictionmarkets.tools/tools/polymarket-us.md) — Polymarket's CFTC-designated US exchange — dollars, KYC, and no on-chain oracle.
- [ForecastEx](https://predictionmarkets.tools/tools/forecastex.md) — Economic and climate contracts on a CFTC exchange that pays interest on your collateral.
- [Robinhood Prediction Markets](https://predictionmarkets.tools/tools/robinhood-prediction-markets.md) — Event contracts in the Robinhood app, routed to four exchanges — one of them its own JV.

## FAQ

### Can a US event exchange raise its trading fee overnight?

The CFTC's regulation allows a fee change of less than 1.00 dollar per contract, other than one tied to market making or trading incentives, without certification or notice to the Commission. Kalshi's own Rule 3.13(e) promises notice when amended fees are filed and no implementation before the self-certification timetable allows. The promise is in the rulebook, not in the regulation.

### How much warning does a rule change on a US exchange get?

Under 17 CFR 40.6 the exchange posts the filing on its website when it files, and the CFTC must receive it at least 10 business days before the change takes effect. If the Commission stays it, a further 90-day review follows with a 30-day public comment period. Emergency rules can take effect first and be filed within 24 hours.

### Can a venue change the source a contract settles on after I have bought it?

Kalshi's Rule 7.2 lets it designate a new source agency and underlying, and change related specifications, after the first day of trading if something affects the reliability or transparency of the existing source, and announce the decision on its website.

### How do I know when an offshore venue has changed its terms?

Usually only by the date at the top. Predict.fun's terms say modified terms are posted with the last updated date at the top and become effective upon posting, and that continuing to use the site after that counts as acceptance.

## Sources

1. [17 CFR 40.6, Self-certification of rules](https://www.ecfr.gov/current/title-17/chapter-I/part-40/section-40.6) — Electronic Code of Federal Regulations, read 2026-10-23
2. [17 CFR 40.2, Listing products for trading by certification](https://www.ecfr.gov/current/title-17/chapter-I/part-40/section-40.2) — Electronic Code of Federal Regulations, read 2026-10-23
3. [KalshiEX LLC Rulebook, version 1.29 (Rules 2.8, 2.17, 3.6, 3.13 and 7.2)](https://kalshi-public-docs.s3.amazonaws.com/regulatory/rulebook/Kalshi%20DCM%20Rulebook%20v.1.29.pdf) — KalshiEX LLC, read 2026-10-23
4. [KalshiEX LLC, Self-certification of Rule Amendment Pursuant to Commission Regulation 40.6(a) (Exchange fee schedule)](https://kalshi-public-docs.s3.amazonaws.com/regulatory/notices/Kalshi%20Fee%20Schedule%20Filing%20for%20Posting.pdf) — KalshiEX LLC, 2022-09-09. Cited as the record of how one fee change was filed and when it took effect, not for the fees it set, which later schedules replaced.
5. [KalshiEX LLC, Exchange Fee Schedule (Perpetual Futures Contracts) Update](https://kalshi-public-docs.s3.amazonaws.com/regulatory/notices/Perpetual%20Futures%20Fee%20Schedule%20Update%20-%20October%2019%202026.pdf) — KalshiEX LLC, 2026-10-19
6. [Terms of Service (section 3, Modifications)](https://docs.predict.fun/terms-of-service) — PDF Labs Limited (Predict.fun), 2025-11-18
7. [Public Fee Schedule](https://public.com/disclosures/fee-schedule) — Open to the Public Investing, Inc., 2026-10-13

*Last updated 2026-10-23. A reference page, corrected in place — not a dated post.*