Kalshi vs Polymarket: Fees, Legality & Which to Use in 2026

If you take prices as they come, Kalshi costs you more. At a 50¢ contract, a taker pays 1.75¢ per contract on Kalshi and 1.50¢ on Polymarket US, a gap of about 14%.

If you post resting orders, the two platforms are not in the same category. Kalshi charges a maker 0.44¢ per contract at that same price. Polymarket US pays a maker 0.31¢. The sign flips. That 0.75¢ swing per contract is larger than the entire taker gap, and it is the part most comparisons skip.

Everything else follows from those two numbers. This piece works through the current fee schedules, where each platform is deeper, and what the state courts have actually done to sports contracts. To skip ahead and convert a contract price to American or decimal odds with fees applied, use the Kalshi & Polymarket calculator.

TL;DR

Kalshi is where the liquidity is, by a wide margin. Polymarket is cheaper, and much cheaper if you are patient enough to rest orders instead of crossing the spread.

The rebates you have read about almost certainly do not apply to you

Polymarket ran a flat 50% taker rebate through April 30, 2026. Comparison articles written in that window quoted an effective taker rate roughly half of Kalshi's, and a lot of them still say so. That promotion is over.

What replaced it, on May 28, 2026, is a tiered program keyed to your prior calendar month of volume:

The entry rung is a quarter of a million dollars a month. If you are trading four figures, your rebate is zero and your effective taker fee is the headline rate. Treat any comparison quoting a 50% discount as describing a different trader than you.

Fee structures: the actual math

Both platforms price fees off the same shape, p × (1 − p), so the cost per contract peaks at 50¢ and falls toward zero as the price approaches 1¢ or 99¢. Only the coefficient differs.

Kalshi

Per the July 2026 fee schedule:

• Taker: 0.07 × C × p × (1 − p), rounded up to the cent
• Maker: 25% of that, or 0.0175 × C × p × (1 − p)

At 50¢ a taker pays 1.75¢ per contract and a maker pays 0.44¢. Worked at 100 contracts and 40¢: taker $1.68, maker $0.42. There is no settlement fee and no fee on profit. ACH deposits and withdrawals are free; wires cost $25 per side and debit adds roughly 2%.

Note that selling before settlement pays the trading fee a second time.

Polymarket US

Per the Polymarket US fee schedule effective July 1, 2026, using Θ × C × p × (1 − p):

• Taker: Θ = 0.06, capping at $1.50 per 100 contracts
• Maker: Θ = −0.0125, a rebate credited at fill, capping at $0.31 per 100 contracts

At 100 contracts and 40¢ a taker pays $1.44 and a maker receives $0.30. Rebates land in your balance at the time of the fill rather than on a weekly cycle.

Notice the coefficient moved the wrong way for traders. It was 0.05 under the old US schedule and is 0.06 now, which is why the Kalshi gap narrowed from something close to half down to 14%.

Polymarket International

Rates vary by category, and makers are never charged at all:

The maker rebate is a share of the fees collected in that specific market, distributed daily, so what you actually receive depends on how much other makers are competing with you in the same book.

Side by side, 100 contracts at 40¢

For a taker, Polymarket US saves you 24¢ on a $40 position. That is real but small, and it is the number most people optimize. For a maker, the swing is 72¢ on the same position and it runs in the opposite direction from the one Kalshi's larger order books would suggest. If you are quoting rather than hitting, that difference compounds far faster than any spread advantage Kalshi gives you back.

After fees, the effective odds on a contract differ from the raw price. The prediction markets calculator does that conversion for both platforms.

Funding and KYC

Kalshi

Dollars in, dollars out, with no crypto at any layer. Deposits run over ACH, debit card or wire. Withdrawals go to a linked US bank account, free, typically one to three business days. Full identity verification comes before the first deposit: legal name, address, date of birth, SSN and a government ID. Native iOS and Android apps.

Polymarket US

Deposits arrive by card or bank transfer through partner providers, and the same partners route funds back out. Identity verification is mandatory under CFTC regulation and covers the same fields Kalshi asks for. Settlement still happens in USDC underneath, but US users never touch a wallet. Web only, with no native app.

Polymarket US removed its waitlist in May 2026, so US access no longer queues.

Polymarket International

The original wallet-native experience. Deposit USDC on Polygon, withdraw to any Polygon-compatible wallet for gas, and skip platform-level KYC entirely, though partner on-ramps may ask for it. Lower friction if you already hold crypto and higher friction if you do not.

Market depth and liquidity

July 2026 was a record month for the sector at $50.6B across the three platforms, up 7.8% from June:

• Kalshi: $37.7B, up 14% month over month
• Polymarket International: $7.9B, down 26%
• Polymarket US: $5.0B, up 54%

Kalshi took roughly 75% of the total and was the only one of the three to grow. That is a genuine shift from 2025, when Polymarket led for most of the year, and the gap is much wider than the near-parity that older comparisons describe.

Two caveats on reading those numbers. The World Cup, which ran June 11 to July 19, distorted everything: Kalshi's market on the final alone drew about $1.9B and Polymarket's tournament-winner market about $4B. And open interest across all three fell from roughly $2B at the start of July to $1.2B by the end as those contracts settled, so the record volume describes a tournament, not a new baseline.

Polymarket US growth also came partly at the international platform's expense once the waitlist lifted, rather than landing entirely on top of it.

Where each tends to be deeper:

Kalshi: US politics, US economic indicators (CPI, jobs, Fed decisions), weather, and an expanding sports book.

Polymarket: global political events, crypto, cultural markets, and niche or experimental questions.

For retail-size trades on core markets, both have enough depth that you will not move the price. Above roughly $10,000, read the order book first.

Where each one wins

Kalshi if you want USD funding with no crypto layer at any depth, if you trade US politics, economics or weather where its books are deepest, if you want a native mobile app, or if you value the longest regulatory track record.

Polymarket if you post resting orders, which is the single biggest cost difference between the two. Also if you trade geopolitical markets, which are free on the international platform, or if you want the wider catalogue of international and cultural questions. If you are outside the US, this is the only one of the two available to you.

Arbitrage between the two

Overlapping markets do diverge. A contract might trade at 0.42 on one platform and 0.45 on the other at the same moment.

Clean arbitrage is harder than it looks, for three reasons: resolution sources and criteria are not always identical, the fee difference moves the breakeven, and both platforms impose position limits.

What works reliably is routing each side to the better venue. If Kalshi prices YES at 0.42 and Polymarket at 0.45, buy YES on Kalshi and take NO on Polymarket at an implied 0.55 rather than 0.58. The prediction markets calculator converts both post-fee prices to comparable odds so you can see which side is actually cheaper.

Legal status, as of September 24, 2026

Federally, both platforms are CFTC-regulated and both operate nationwide. Kalshi has held a Designated Contract Market license since November 2020. Polymarket acquired QCEX, a licensed DCM and clearinghouse, in July 2025 and relaunched for US users on December 2, 2025.

The fight is narrower than "are prediction markets legal." It is specifically about sports event contracts, and it is unresolved in a way that now affects which markets you can see. Each platform has its own page for the detail: is Kalshi legal and is Polymarket legal in the US.

The federal appeals courts have split. On April 6, 2026 the Third Circuit sided with Kalshi, holding its sports contracts are likely swaps under the Commodity Exchange Act. On August 28 the Ninth Circuit ruled 3-0 the other way in Nevada's dispute with Kalshi, Crypto.com and Robinhood, finding the contracts are sports gambling rather than swaps. New Jersey has asked the Supreme Court to take up the question, and Robinhood and Crypto.com have filed petitions of their own. Kalshi has asked the full Ninth Circuit to rehear its case.

Court orders now block Kalshi's sports contracts in Nevada, Washington and Michigan, and courts have sided with the state in Ohio, New York, Connecticut, Utah, Iowa and Maryland. Kalshi still holds the upper hand in New Jersey, Tennessee, Arizona and Minnesota, where federal injunctions stop enforcement, and Massachusetts's injunction is paused while the state's highest court decides the appeal. Polymarket's exposure is newer but growing: New York sued Polymarket US on September 24, and Missouri sent both platforms cease-and-desist letters in September.

Practically: your access to sports markets specifically depends on your state and can change between one week and the next. Non-sports markets are largely untouched by all of this. Nothing here is legal advice, and the position moves fast enough that you should check the current status where you live rather than trusting any article, including this one.

Tax treatment

Both platforms create taxable events on profit, and both CFTC-regulated venues issue tax forms. Kalshi issues a 1099-B reporting activity as trading rather than gambling. Polymarket US issues 1099 reporting under its post-QCEX status. Polymarket International issues nothing, leaving users to track USDC-denominated trades themselves.

Whether that activity is then ordinary income or capital gains is unsettled and can depend on the contract. See our full breakdown of Kalshi and Polymarket taxes for the detail. Not tax advice; talk to a CPA who handles derivatives clients.

Which to pick

Answer one question first: do you cross the spread or do you rest orders?

If you take prices, the platforms are close enough that fees should not decide it. Pick on market selection and funding. Kalshi for US politics, economics and weather in dollars with an app. Polymarket for global events, crypto and culture.

If you rest orders, Polymarket pays you to provide liquidity and Kalshi charges you for it. That is worth more than any of the other differences here, and it points one direction.

Plenty of active traders keep accounts on both and route each trade to whichever venue prices it better after fees. Given the two fee schedules now sit within 14% of each other on the taker side, that is less about the platforms and more about the specific market in front of you.

Verify the math before you trade

The most common mistake on prediction markets is reading the contract price as final odds. Buy 100 contracts at 40¢ and you are not getting +150. On Polymarket US the fee takes you to +141; on Kalshi, +140.

Those two numbers are worth sitting with, because they are one point apart. On the taker side the platform you choose barely registers once you express it as odds, which is the whole reason the maker side above deserves more of your attention than it usually gets.

Use the Kalshi & Polymarket calculator to convert contract prices to American, decimal or fractional odds with fees applied, and to compare the two platforms side by side against sportsbook prices on the same market.

Sources

• Kalshi Fee Schedule, July 2026
• Polymarket US Fee Schedule, effective July 1, 2026
• Polymarket Trading Fees documentation
• Kalshi and Polymarket July volume, The Block
• Ninth Circuit opinion, KalshiEX v. Assad, August 28 2026
• Connecticut ruling on Kalshi sports contracts, August 10 2026
• New York sues Polymarket, Governor's office, September 24 2026
• Prediction markets legal timeline, RotoWire