- The Fee Basis
- Maker Fees and Resting Orders
- Why Markets Differ
- How Polymarket Charges Instead
- Which Is Cheaper?
- The Full Cost of a Round Trip
- A Worked Example of Fee Drag
- Why Frequency Multiplies the Cost
- How to Check the Fee on Your Trade
- Why This Decides Whether an Edge Exists
- Fees Inside a Cross-Venue Comparison
The Fee Basis
Kalshi's revenue model is a transaction fee charged on the expected earnings of a contract. The company states plainly that it earns from fees rather than from taking a position in the outcomes it lists — which is why the fee applies to a trade whether or not your side ultimately wins.
Kalshi publishes a complete fee schedule along with the mathematics behind the fee, and links it from its own help centre. Because the schedule is revised over time and contains market-level detail, this page deliberately does not restate a numeric rate: read the published schedule and the fee displayed in the order ticket for the market in front of you.
Where to see it in the interface: Kalshi's help centre states the fee for a trade can be seen by clicking the “i” icon to the right of the “You're buying” panel in the order ticket. That figure is authoritative for that order — a general schedule is not.
Maker Fees and Resting Orders
Some Kalshi markets carry maker fees. Kalshi documents the mechanism precisely:
- A maker fee applies to an order that is not immediately matched and instead rests on the orderbook.
- The fee is charged only when the trade is ultimately executed — not at the moment the order is placed.
- There is no fee for cancelling a resting order.
Two consequences follow. First, placing a limit order is not automatically free on Kalshi the way a resting maker order is on Polymarket — check whether the specific market carries a maker fee before you assume. Second, because cancelling carries no charge, there is no penalty for revising a stale quote; the cost only crystallises on execution.
| Order behaviour | Kalshi | Polymarket |
|---|---|---|
| Order crosses immediately (taker) | Transaction fee on expected earnings | Taker fee = shares × feeRate × price × (1 − price) |
| Order rests on the book (maker) | Maker fee on some markets, charged only if executed | No fee |
| Cancelling a resting order | No fee | No fee |
| Market-specific variation | Yes — special events can carry different fees | Yes — category determines the taker fee rate |
| Fee charged when the trade loses | Yes | Yes — charged at match, not at settlement |
| Settlement currency | USD | USDC |
Why Markets Differ
Kalshi states that some markets have fees that differ from others, and attributes this to special events — it names elections, awards ceremonies, and large sporting championships as examples. The practical reading is that you cannot carry a fee assumption from one market to the next, even within the same category.
This is a structural feature of a regulated exchange listing many distinct contract types, not an anomaly. It means the fee belongs on your pre-trade checklist alongside the closure type and the resolution source. See How Kalshi Works for the rest of that checklist.
How Polymarket Charges Instead
Polymarket's published taker fee is not a flat percentage. The protocol formula is:
fee = shares × feeRate × price × (1 − price)
The shape of that expression matters more than its constants. Because it includes both price and (1 − price), the fee is largest at a 50¢ price and falls toward both extremes. A contract at 50¢ carries the maximum fee for its category; the same size at 95¢ or 5¢ carries far less. The rate itself depends on the market category, with crypto markets rated higher than politics and geopolitics rated at zero in the figures published on this site.
Two further differences are decisive for cost per round trip: makers who rest limit orders pay nothing, and the fee is charged at match time rather than at settlement. A Polymarket trade that goes on to lose still paid its fee at execution.
Which Is Cheaper?
There is no universal answer, and any article claiming otherwise is comparing headline numbers that do not apply to your trade. The two platforms charge on genuinely different bases:
| Your situation | What to check |
|---|---|
| Mid-priced contract (near 50¢) | Polymarket's taker fee peaks here; compare it directly against Kalshi's fee for the same market |
| Extreme-priced contract (under 10¢ or over 90¢) | Polymarket's taker fee shrinks sharply; Kalshi's basis is different, so the gap can invert |
| You can rest a limit order | On Polymarket a maker pays nothing; on Kalshi confirm whether that market carries a maker fee |
| High trade frequency | Fee per trade compounds — model the whole sequence, not one fill |
| Large size | Spread and slippage will likely outweigh the fee difference entirely |
Do the arithmetic on the price you can actually get. A fee difference of a fraction of a cent per share is irrelevant if you are crossing a 4¢ spread. Spread first, fee second — never the reverse.
The Full Cost of a Round Trip
The quoted fee is only one of several costs sitting between your probability estimate and your realised return, and they behave differently. On a fee page it is easy to forget that the fee may not even be the largest of them:
| Cost component | Where it appears | When it is incurred |
|---|---|---|
| Spread (bid–ask) | The order book, before any fee | Every time you cross it |
| Entry fee | Order ticket / published schedule | When the entry executes |
| Exit spread | The order book, on the closing order | If you close before resolution |
| Exit fee | Order ticket for the closing order | When the close executes |
| Settlement | No order is placed | At resolution, if held to expiry |
The structural point is that a position held to settlement pays one entry fee and no exit cost, because there is no second order to place. A position that is closed early pays a second execution plus a second crossing of the spread. Closing early has to earn its keep.
Why this surprises people: a trade looks fee-cheap in isolation, and expensive only once you count the leg you did not plan for. The entry was never the whole cost.
A Worked Example of Fee Drag
Assume, purely so the arithmetic is visible, that the applicable transaction fee works out to 1¢ per contract at the price you are trading. Your model values the contract at 55% and you can buy it at 52¢.
Held to settlement: 3¢ − entry fee (1¢) = 2¢ net
Closed early at the same price: 3¢ − two executions (2¢) = 1¢ net, plus two crossings of the spread
Two conclusions follow directly from those lines. First, the fee consumes a third of a three-point edge on a held position and two thirds of it on a round trip. Second, at a 2¢ edge the same round trip is 3¢ − 2¢ − 2¢ = negative, and the trade loses money even if your 55% estimate turns out to be exactly right.
The 1¢ figure is a stated assumption, not a quote of Kalshi's rate. It exists so the arithmetic can be followed. Substitute the figure shown in your own order ticket: if the fee plus the spread exceeds your raw edge, the trade is a loser before resolution.
Why Frequency Multiplies the Cost
A transaction fee is charged per execution, so its total cost scales with how often you trade, not with how confident you are on any single trade. Holding the same 1¢ assumption and the same size:
| Executions per contract | Cumulative fee per contract | Compared with |
|---|---|---|
| 1 | 1¢ | 1% of the $1.00 maximum payout |
| 10 | 10¢ | 10% of the maximum payout |
| 100 | $1.00 | Equal to the maximum payout of the contract itself |
That last row is the one worth remembering: an active trader can pay, in fees alone, the entire face value of the contract they are trading. A thin edge taken a hundred times is not one thin edge — it is a hundred opportunities for a fee to erase it. This is why high-frequency fee-sensitive strategies live or die by their cost line rather than by their signal quality.
How to Check the Fee on Your Trade
- Open the market's page and read its rules summary and closure type.
- Build the order in the ticket and click the “i” icon next to “You're buying” to see the applicable fee.
- Consult Kalshi's published fee schedule for the market's fee basis.
- Record the fee as a percentage of your stake, not as an abstract rate — that is the number that interacts with your edge.
On Polymarket, the equivalent step is reading the category rate for the market and applying the formula above to your intended size, then checking the book so you know the spread you are crossing.
Why This Decides Whether an Edge Exists
A fee is not a nuisance cost bolted onto a trade — it is a direct reduction of your edge, and at small edges it is the difference between a positive and a negative expectation. Suppose your model says a contract is worth 55% and you can buy it at 52¢. Your raw edge is three points. If the combined cost of spread and fee exceeds three points, the trade is a loser no matter how correct your probability estimate turns out to be.
This is why fee mechanics matter most to exactly the trades that look safest: thin edges taken repeatedly. Model it directly in the Cross-Platform Edge Calculator, which subtracts both platforms' fee bases from a quoted gap, or size the position with the Kelly Calculator once you know the true net edge.
Fees Inside a Cross-Venue Comparison
Once the same topic is available on more than one venue, the question changes from “which platform is cheaper” to “does the quoted gap survive both cost structures”. A gap that looks like an edge at headline prices can vanish once the entry fee, the closing fee and the two spreads are subtracted.
Work it in this order:
- Confirm the two markets are the same question — resolution source, date, and the exact threshold. Similar topics are not the same contract.
- Read both order books at the size you intend to trade. The quoted price is for the top of book, not for your order.
- Subtract both fee bases — Kalshi's transaction fee as shown in the order ticket, Polymarket's taker fee from the published formula above.
- Model the exit, or decide deliberately to hold to resolution and remove it.
The Cross-Platform Edge Calculator runs those steps and shows the figure that matters: the gap remaining after costs. For the wider discipline behind it, see Prediction Market Arbitrage and Implied Probability Explained.
Where a Fee Hurts Most
Read the companion pages: Cross-Platform Edge Calculator, Expected Value Calculator, Kalshi vs Polymarket and the Kalshi Hub.
Compare Both Fee Bases →Frequently Asked Questions
Does Kalshi charge a fee if I lose the trade?
Yes. The fee is a transaction fee charged on execution, not a cut of winnings — so it applies to a trade that goes on to resolve against you, just as Polymarket's taker fee is charged at match time.
Is placing a limit order on Kalshi free?
Not necessarily. Some Kalshi markets carry maker fees on orders that rest on the orderbook. The fee is charged only if the resting order ultimately executes, and there is no fee to cancel it.
Why doesn't this page list Kalshi's exact fee rate?
Because the schedule is published by Kalshi and varies by market, and restating a number here would risk being stale and wrong for your specific trade. The authoritative figure is the one shown in your order ticket and the published schedule. We would rather point you to the source than print a rate that might not apply.
Is Polymarket's taker fee highest at 50¢?
Yes — that is a direct consequence of the formula shares × feeRate × price × (1 − price). The product of price and its complement peaks at 50¢, so the fee does too, and it declines as the price moves toward either extreme.
Should I choose a platform based on fees alone?
No. Eligibility, custody model, funding rails, market availability and liquidity depth will usually matter more. Fees decide whether a specific thin-edge trade is worth taking, not which platform suits you overall.
Is it cheaper to hold a position to settlement than to close it early?
On cost alone, holding avoids one execution and one crossing of the spread, so it is the cheaper path — the entry fee is paid either way. That does not make it the better path: holding also keeps your capital exposed until resolution, so the comparison is cost against optionality, not cost against nothing.
Am I charged on both the entry and the exit?
Kalshi's fee is described as a transaction fee charged on execution, so an entry and an exit are two separate executions. A closed round trip therefore faces two fee events plus two spreads, while a position held to settlement faces one fee and no exit spread.
Does a higher fee always make a market the worse choice?
No. Order of importance is spread first, fee second. A market with a slightly higher fee inside a 1¢ spread can be cheaper than a low-fee market that forces you to cross 5¢ to get filled, and a deep book also lets you exit at a better price when you need to.
Run the Real Numbers
Enter prices from both platforms and your size — see whether the gap survives both fee bases and the spread.
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Open Polymarket →Running a Rules-Based Process?
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