Inside the Suspicious-Bet Surge on Kalshi and Polymarket

Update — August 17, 2026. Re-verified platform availability, promo terms, and New York eligibility against each operator's own published pages this week. Where an operator has changed its terms, the copy below reflects the current version.

Prediction-market volume is the highest it has ever been, and so is the share of trades that get a second look. Reuters reported on Tuesday that [Kalshi](=AFF:kalshi) and [Polymarket](=AFF:polymarket) are both grappling with a surge of suspicious bets — flagged trades that the platforms suspect may involve insider information, coordinated activity, or front-running of news that hasn't broken yet.

For a New Yorker who trades on either platform, this isn't an abstract compliance story. It changes how fast markets resolve, how much the platforms cooperate with regulators, and how the next round of the CFTC vs. New York fight is going to be argued.

Update — July 2, 2026. Both platforms have rolled out new surveillance disclosures since the May Reuters story: Kalshi added a public market-integrity page summarizing its SAR cadence, and Polymarket tightened wallet-level position limits on event contracts tied to non-public news flow (sports injuries, regulatory filings, indictments). Albany's licensing bill cleared committee in mid-June — the political pressure the original story flagged has only intensified.

What is a suspicious trade on a prediction market?

A suspicious trade is any position large enough or timed precisely enough that the platform's surveillance system flags it for review. The classic example: a wallet that loads up on a contract minutes before a news event — a Fed decision, an indictment, a sports injury report — that moves the price hard in their favor. On a stock exchange that's insider trading; on a prediction market the legal framing is messier, but the platforms still investigate.

Both Kalshi and Polymarket run automated surveillance. Kalshi, as a CFTC-regulated designated contract market, files Suspicious Activity Reports when warranted. Polymarket — built on a public blockchain — can trace wallets but has historically relied more on community signals and post-hoc clawbacks than on real-time interdiction.

Why the flagged-trade volume is rising now

• —Non-sports event-contract volume on Kalshi just crossed $1B in a week. More volume means more flagged tail activity, mechanically.
• —Polymarket's reentry to the U.S. market through its iOS app brought a new wave of traders — and more sophisticated actors looking for edge.
• —JPMorgan and surveillance startup Hadrius have started selling compliance tooling to prediction-market platforms, which means more flags get raised, not necessarily that more crime is happening.
• —Regulators in Albany and Washington are watching closely, so the platforms are erring on the side of flagging and disclosing rather than missing something.

What this means for a New York trader

Three practical effects. First, resolution on disputed markets can take longer — if a market becomes the subject of a surveillance review, payouts can be paused while the platform investigates. Second, large positions in thinly traded markets are likelier to attract a compliance ping (which is usually nothing, but it's a process). Third, the platforms' willingness to share data with regulators is now a competitive feature, not a liability.

Why Albany cares

New York's push to regulate prediction markets is partly a turf war with the CFTC, and partly a consumer-protection argument. Every Reuters story about flagged trades makes the state's case easier to argue: if the markets need surveillance, the question becomes who does the surveilling, and who licenses the surveillor.

The Trump administration has so far defended prediction markets as legitimate financial instruments. Albany is testing how durable that defense is — and the suspicious-trade headlines are the pressure test.

The bottom line

Higher volume produces more flags. More flags produce more headlines. More headlines produce more political pressure. None of it makes the markets illegal in New York today, and none of it should change how a casual trader uses them. But it does mean the platforms are operating under a brighter spotlight — and the regulatory calendar in Albany just got more interesting.

Editorial only — not a recommendation to trade. Compare the two main platforms on our Kalshi review and Polymarket review pages.