Kalshi is a CFTC-designated contract market that settles in US dollars, while Polymarket runs two distinct venues: an international order book that settles onchain on Polygon, and Polymarket US, a CFTC-designated contract market of its own. For an institutional desk the practical differences come down to who can access which venue, how collateral is held and settled, and how each API is built. Many desks end up trading both, and the operating question becomes how to keep the two in one book.

Regulation and access

Kalshi operates through KalshiEX LLC, which the CFTC designated as a contract market in 2020, and its trades clear through Kalshi Klear, its affiliated clearing organization. Institutions can trade directly, clear through an FCM that is a member of Kalshi’s exchange and clearinghouse, or qualify as self-clearing members. Kalshi also accepts traders from many countries outside the US, subject to the restricted-jurisdiction list in its Member Agreement.

Polymarket’s position is more layered. The international platform operates offshore, and the API exposes a geoblock check because order placement is restricted from certain jurisdictions, including the United States. For the US market, Polymarket acquired QCEX, now QCX LLC doing business as Polymarket US, a CFTC-designated contract market with its own clearinghouse, QC Clearing LLC (d/b/a Polymarket Clearing). In November 2025 the CFTC approved an amended order of designation allowing intermediated access through FCMs, and on November 3, 2026 Polymarket announced that its FCM, PM Derivatives, had received NFA approval, and said it will operate on a fully collateralized basis. Before trading, a desk needs to establish which Polymarket it is eligible for, because the two venues have separate onboarding, separate rulebooks and separate order books.

Settlement and collateral

Kalshi event contracts are dollar-denominated and fully collateralized. The full cost of a position is posted at the time of the trade and the contract pays out in dollars on resolution, so there is no variation margin cycle on event contracts.

Polymarket’s international venue uses a hybrid design. Orders are signed messages matched offchain by an operator, then settled atomically onchain on Polygon. Since the CLOB V2 migration in April 2026 the collateral token is pUSD, an ERC-20 on Polygon backed by USDC, and positions are held as outcome tokens in the trader’s own wallet. Polymarket US settles in US dollars on a pre-funded basis, with accounts funded by wire. The treasury implication is real: the international venue means stablecoin operations and wallet custody, while Kalshi and Polymarket US look like any other dollar-funded futures relationship.

Market coverage

Both venues list binary event contracts priced between zero and one dollar across economics, politics, crypto, sports and culture. Kalshi lists macro releases, Fed decisions and dated crypto price levels that line up naturally against a derivatives book, and since May 2026 it has also listed margined perpetual futures on crypto, stocks, metals and indices. Polymarket’s international venue is known for breadth and speed of new listings, including short-dated crypto up/down markets. Polymarket US lists contracts it self-certifies with the CFTC, so its catalogue is a separate list that does not mirror the international one. Desks should check contract terms market by market, since resolution sources and timing differ even when two contracts describe the same event.

API surfaces

Kalshi offers a REST trading API, WebSocket feeds and a FIX gateway on FIX 5.0 SP2, with keys authenticated by RSA or Ed25519 signatures. RFQ is available over REST, FIX and WebSocket: a requester broadcasts a request to makers on any market, including combo markets, and accepts a quote. More detail is in our Kalshi API guide for institutional desks.

Polymarket international exposes the Gamma API for market discovery, the CLOB REST API for order books and orders, and WebSocket market and user channels. Authentication has two layers: a wallet signature to derive credentials, then HMAC-signed requests, with every order itself signed by the wallet under EIP-712. Polymarket US is a different stack, with REST, gRPC streaming and FIX over a private AWS connection, plus RFQ on any listed instrument, including combos. Our guide to Polymarket for institutional traders walks through both setups.

Liquidity shape

Both venues run central limit order books, and on both the depth concentrates in headline events and near-dated contracts. Long-dated and niche markets can show a reasonable top of book with little behind it. Kalshi’s RFQ and block-trading channels exist for size that would move the screen, and Polymarket US publishes block-trade rules for eligible contract participants. On Polymarket’s international venue, some crypto and finance up/down markets apply a short taker delay before matching, which changes how aggressive orders behave. Our block trading guide for Kalshi and Polymarket covers how desks handle size on each.

Operational setup

• Kalshi: entity onboarding with Kalshi or through an FCM member, dollar funding, API keys generated in the account and FIX access arranged with the institutional team.
• Polymarket international: a Polygon wallet (an EOA or a Safe proxy wallet), pUSD collateral, token approvals for the exchange contracts, and API credentials derived from the wallet signature.
• Polymarket US: an institutional application through the Polymarket portal, wire funding, RSA API keys for REST and gRPC, and a VPC PrivateLink connection if FIX is required.

The international venue asks the desk to run key management for a signing wallet. Kalshi and Polymarket US look like conventional exchange relationships with compliance onboarding up front.

Running Kalshi and Polymarket in one book with Kemet

Kemet treats both venues as part of one platform. Desks connect their own Kalshi and Polymarket accounts with their own API keys, and Kemet never holds funds or acts as counterparty. From there, discovery puts the markets from both venues next to each other and next to the listed derivatives the desk already trades. Execution runs from one ticket or one REST and WebSocket API, with time-sliced and iceberg-style algorithms and smart routing across venues when Kalshi and Polymarket list economically similar contracts, after checking that each venue’s resolution source and timing match closely enough for the desk’s purposes. Position management puts Kalshi and Polymarket positions in one portfolio and risk view with crypto options, perpetuals, futures and spot on Deribit, OKX, Binance, Coinbase, Bullish, Hyperliquid and Derive.

That matters most when the two venues disagree. If a Kalshi contract and a Polymarket contract on a similar BTC level trade at different probabilities, an eligible desk can see both and trade the difference, treating the different settlement indices and times as basis risk, and hedge the residual with Deribit options without leaving the platform. That workflow is laid out in hedging Kalshi and Polymarket crypto contracts with Deribit options. The hub page on institutional prediction markets trading covers the rest, including the FalconX, Kalshi and Kemet collaboration announced in August 2026.

FAQ

Is Polymarket regulated in the US?

Polymarket US, operated by QCX LLC, is a CFTC-designated contract market with its own clearinghouse. Polymarket’s international platform is a separate venue that operates offshore and restricts order placement from certain jurisdictions, including the United States.

Which venue settles in stablecoins?

Polymarket’s international venue settles onchain on Polygon using pUSD, which is backed by USDC. Kalshi and Polymarket US settle in US dollars.

Does Kalshi support FIX and RFQ?

Yes. Kalshi offers a FIX gateway alongside REST and WebSocket, and its RFQ workflow runs over all three.

Can one desk trade both venues from one system?

Yes. Through Kemet a desk connects its own Kalshi and Polymarket accounts and trades both from one UI and one API, with positions in a single risk view alongside its crypto derivatives.

Running Kalshi and Polymarket side by side is easier to judge on your own markets than on paper. Book a demo and we will show both venues in one book next to your derivatives positions.