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

The prediction markets landscape changed in late 2025. Polymarket returned to US users on December 2, 2025 after a three-year hiatus, which means the old answer to "Kalshi vs Polymarket" (Kalshi if you're American, Polymarket if you're not) no longer applies. Both platforms are now CFTC-regulated, both are accessible to US traders, and the choice between them comes down to fees, market selection, and how you want to fund your account.

This breaks down what each platform actually charges, where each one wins on liquidity, and how to decide which to use. To skip the analysis and convert a contract price to American or decimal odds with fees applied, use the Kalshi & Polymarket calculator.

TL;DR

If you're in the US and want the simplest, USD-native experience, Kalshi is straightforward. If you want lower fees on most markets, Polymarket US is competitive after its 50% taker rebate (currently active through April 30, 2026). State-level legal challenges affect both platforms unevenly depending on where you live.

Both are now CFTC-regulated

This is the biggest shift since most older comparison articles were written. Until late 2025, Polymarket had been geo-blocked from US users since a 2022 CFTC settlement. That ended when Polymarket acquired QCEX, a CFTC-licensed Designated Contract Market and clearinghouse, for $112 million in July 2025. The CFTC granted Polymarket an Amended Order of Designation in November 2025, and the platform relaunched for US users on December 2, 2025.

Kalshi has held a CFTC Designated Contract Market license since November 2020 and publicly launched in July 2021. The platform has consistently operated under federal oversight.

Federal approval doesn't mean every state agrees. Both platforms face active state-level lawsuits arguing that sports event contracts function as illegal sports betting. As of early 2026, Kalshi has been challenged in Massachusetts, New York, Wisconsin, Arizona, Michigan, Nevada, and Washington. Massachusetts issued a preliminary injunction in January 2026 requiring Kalshi to geofence Massachusetts users from sports markets. Nevada filed a similar complaint against Polymarket in January 2026. Both platforms argue federal CFTC oversight preempts state gambling laws; that question is still being litigated.

Practical impact: depending on your state, you may be unable to access certain market categories (especially sports event contracts) on either platform. Federal legality is settled. State-by-state availability is not.

Fee structures: the actual math

This is where the platforms diverge most. Both use a per-contract fee model that scales with contract price, but the formulas differ.

Kalshi fees

Kalshi charges fees per contract, with the rate depending on whether you're a taker (executing against an existing order) or a maker (placing a resting order):

• Taker fee = round up of 0.07 × C × P × (1 − P) per trade, where C is the number of contracts and P is the price in dollars
• Maker fee = 25% of the taker fee, or 0.0175 × C × P × (1 − P)

The fee maxes out when P = 0.50 (peak uncertainty). At that point a taker pays 1.75¢ per contract; a maker pays 0.44¢ per contract. The fee falls symmetrically toward 0 as the contract price approaches 0¢ or 99¢.

Worked example: 100 contracts at 40¢

• Taker fee: 0.07 × 100 × 0.40 × 0.60 = $1.68
• Maker fee: 0.0175 × 100 × 0.40 × 0.60 = $0.42

There are no separate "fee on profit" or "fee on settlement" charges. You pay the fee once at execution. Kalshi withdrawals to your linked bank are free.

Sources: Kalshi fee schedule (PDF, Feb 2026), Kalshi help center.

Polymarket fees

Polymarket also charges per-contract fees with a similar p × (1 − p) shape, but the rate depends on the market category. Per Polymarket's documentation:

Formula: fee = C × feeRate × p × (1 − p)

The US version (Polymarket US, post-QCEX) currently uses a flat 0.05 taker coefficient with a 0.0125 maker rebate and a 50% taker rebate active through April 30, 2026, paid weekly. So an effective US taker rate during the rebate period is about 0.025.

Worked example: 100 contracts at 40¢ in a US sports market with the rebate

• Base taker fee: 100 × 0.05 × 0.40 × 0.60 = $1.20
• Effective with 50% rebate: $0.60

Polymarket does not charge withdrawal fees. Geopolitical and world-event markets are entirely fee-free across both versions.

Side-by-side fee comparison

For a 100-contract trade at 40¢:

For prices between 30¢ and 70¢ on most market categories, Polymarket is cheaper than Kalshi, often by 30 to 60 percent. The gap is largest on geopolitical markets (where Polymarket is free) and narrowest on crypto markets (where Polymarket is more expensive than Kalshi). The current Polymarket US rebate amplifies that gap until April 30, 2026.

After fees, the effective odds you get on a contract differ from the raw price. The prediction markets calculator does this conversion automatically across both platforms.

Funding and KYC

Both platforms require KYC for US users. The funding mechanics differ.

Kalshi

• Deposit: ACH bank transfer, debit card, or wire transfer
• Withdrawal: ACH to your linked US bank account, free, typically 1 to 3 business days
• KYC: Full identity verification (legal name, address, date of birth, SSN, government ID upload) before your first deposit
• Currency: USD throughout. No crypto involved.
• Mobile app: Native iOS and Android

This is the friction-free path if you don't want to touch crypto. Money goes from your bank to Kalshi to your trades and back, in dollars.

Polymarket (US)

• Deposit: Credit card, debit card, or bank transfer through partner providers (MoonPay, Robinhood Connect, Coinbase Pay)
• Withdrawal: Same partners route USDC back to fiat
• KYC: Full identity verification (name, DOB, address, SSN, government ID), required by federal law under CFTC regulation
• Currency: USDC under the hood (a USD-pegged stablecoin on the Polygon network), but for US users the platform abstracts this away. You deposit dollars; Polymarket handles the conversion.
• Mobile: Web only (mobile-friendly site, no native app)

Behind the scenes Polymarket still settles in USDC, but US users no longer need a crypto wallet. The trade-off is that fiat off-ramps go through partner providers like MoonPay, each with their own KYC and fees.

Polymarket (international)

For users outside the US, Polymarket remains a wallet-native platform:

• Deposit: USDC on Polygon, sent to your Polymarket-linked wallet
• Withdrawal: USDC to any Polygon-compatible wallet (gas fee only)
• KYC: None for the wallet flow itself; partner on-ramps may require it
• Currency: USDC

This is the original Polymarket experience: lower friction if you already hold crypto, higher friction if you don't.

Market depth and liquidity

Volume tells you how much money is flowing through each platform, which is roughly proportional to how much you can trade without moving the price. As of mid-2026:

• April 2026 monthly volume: Kalshi $14.81B, Polymarket ~$9B
• YTD through April 20, 2026: Kalshi ~$37.49B, Polymarket ~$29.23B
• 2026 valuation: Kalshi $22B (March 2026 round); Polymarket reportedly targeting $15B

Kalshi has pulled ahead in raw monthly volume in 2026 after Polymarket fell 14.8% from March to April. That's a recent shift; for most of 2025 Polymarket led. Both platforms are growing year-over-year in absolute terms.

Where each platform tends to be deeper:

Kalshi:

• US politics (presidential, congressional, state-level)
• US economic indicators (CPI, jobs reports, Fed rate decisions)
• US weather and climate events
• Recently expanded sports markets (championship-tier events)

Polymarket:

• Global political events (UK, EU, geopolitical)
• Crypto markets (BTC price levels, ETH events, exchange-specific)
• Cultural events (Oscars, Grammys, viral predictions)
• Niche or experimental markets

For typical retail-size trades ($10 to $1,000) both platforms have enough depth on their core markets that you won't move the price. For $10,000+ positions, watch the order book before placing.

Sources: QuantVPS prediction markets volume, DeFi Rate prediction market volume tracker.

When Kalshi beats Polymarket

1. You want USD funding without any crypto layer. Kalshi is dollars in, dollars out, even behind the scenes.
2. You're trading US-specific markets. Politics, economics, weather. Kalshi has more participants and tighter spreads here.
3. You want a native mobile app. Kalshi has iOS and Android; Polymarket is web only.
4. You value the longest regulatory track record. Kalshi has been a CFTC DCM since 2020.
5. You're trading low-priced longshots (under 15¢). Both platforms have similar fee curves at extremes, but Kalshi's per-trade calculation is more predictable.

When Polymarket beats Kalshi

1. You want lower fees on mid-priced contracts. Polymarket's rates are 30 to 60 percent lower than Kalshi's on most categories at prices between 30¢ and 70¢.
2. You're trading geopolitical or world-event markets. Polymarket charges no fee on these.
3. You want a wider catalog. Polymarket's market selection is broader, especially for international and cultural events.
4. You're already in the crypto ecosystem. International Polymarket lets you trade with USDC and skip fiat partners entirely.
5. You're outside the US. Polymarket is accessible to users in most jurisdictions outside the US (subject to local restrictions); Kalshi is US-only.

Arbitrage between Kalshi and Polymarket

Both platforms now list overlapping markets, especially on US politics and major events. Prices can diverge: a "Will X win the election" contract might trade at 0.42 on Kalshi and 0.45 on Polymarket simultaneously.

You can't always cleanly arbitrage between them because:

• The two platforms can have slightly different resolution sources or criteria
• Fee differences mean the breakeven price differs across platforms
• Both have KYC and per-platform position limits

But you can pick the better-priced platform for whichever side you want. If Kalshi prices YES at 0.42 and Polymarket prices YES at 0.45, take YES on Kalshi. If you want NO, take it on Polymarket where the implicit NO price is 0.55 instead of 0.58.

This is routine for sharper traders. The prediction markets calculator converts each platform's price (post-fees) to comparable American or decimal odds so you can see which is cheaper before you trade.

Tax treatment (US)

Both platforms generate taxable events on profit. As CFTC-regulated venues, both now issue tax forms:

• Kalshi issues a 1099-B at year-end for active US traders. Profits typically reported as short-term capital gains depending on the contract type.
• Polymarket US issues 1099 tax reporting under its CFTC-licensed status (post-QCEX). The platform handles US tax compliance for accounts opened through the US version.
• Polymarket international doesn't issue tax forms. Users are responsible for tracking USDC-denominated trades and reporting them.

Treatment as gambling income vs. capital gains depends on the contract type and your specific tax situation. This is not tax advice; consult a CPA who handles prediction-market or derivatives clients.

Which platform to pick

Pick Kalshi if:

• You're in the US and want the simplest USD funding flow
• You're primarily trading US politics, economics, or weather markets
• You want a native mobile app
• You don't want to touch crypto or stablecoins at any layer

Pick Polymarket (US) if:

• You're in the US and want lower fees on most markets
• You're interested in geopolitical or world-event markets (which are fee-free)
• You're comfortable with a web-only interface
• You want broader market selection beyond US-specific events

Pick Polymarket (international) if:

• You're outside the US
• You already hold USDC or are in the crypto ecosystem
• You want zero KYC at the platform level

Trade on both if you can: many active traders run accounts on both platforms to capture the better price on overlapping markets. Watch the spread on shared markets and route trades to whichever platform offers a better effective price after fees.

Verify the math before you trade

The biggest mistake on prediction markets is treating contract price as final odds. A contract at 0.40 on Polymarket sports (with the current US rebate) translates to about +144 American odds after fees. The same contract at 0.40 on Kalshi translates to about +148. That difference compounds over many trades.

Use the Kalshi & Polymarket calculator to convert contract prices to American, decimal, or fractional odds with fees applied. It supports both platforms and lets you compare effective odds side by side, including against sportsbook prices on the same market.

Sources

• Polymarket - Wikipedia
• Kalshi - Wikipedia
• Polymarket Trading Fees Documentation
• Kalshi Fee Schedule (PDF, Feb 2026)
• Polymarket CFTC Approval Press Release (Nov 2025)
• QuantVPS Prediction Markets Volume Comparison (2026)