Portugal Prohibits Polymarket Following €4 Million Insider Trading Controversy

Portugal's gaming regulator has banned the cryptocurrency prediction platform Polymarket due to suspicious trading behaviors linked to the country's presidential election. In the hours leading up to the election results, a staggering €4 million was wagered in just two hours.

Key Takeaways

Portugal’s gaming regulator has banned Polymarket due to alleged insider trading linked to the presidential election.
Over €4 million was wagered before the election results were officially announced.
The SRIJ cited breaches of national laws prohibiting political betting as the reason for the ban.
Insider trading concerns on prediction markets have become more prominent nationally and internationally.
Competing platform Kalshi follows stricter KYC regulations and is making its mark in the prediction market space.

Portugal Bans Polymarket Over €4M Insider Trading Scandal

The Portuguese Gaming Regulation and Inspection Service (SRIJ) ordered the platform to halt its operations and take steps for a blocking after concluding that its activities breached national laws against political betting.

This issue arose amid significant fluctuations in betting odds at the same time that exit polls were shared privately, raising alarming questions about potential insider trading within prediction markets.

Investigation Triggered by Suspicious Betting Patterns

Reports from the Portuguese news outlet Renascença indicate that as the presidential election approached, António José Seguro’s odds stood at 60% on Polymarket, while his opponent, André Ventura, had only a 30% chance of winning.

By 6 PM, just one hour before voting closed, Seguro’s likelihood surged to 96%, and ultimately reached 100% once official projections confirmed his victory.

Portugal Bans Polymarket - Polymarket Prediction Image

This timing further deepened suspicions regarding betting on the next President of the Republic.

At 6:30 PM, Seguro’s odds dramatically jumped from 68.6% to 93.2% within that hour. Concurrently, Cotrim de Figueiredo’s odds plummeted from 22% to just 2.5%, culminating in Seguro being positioned at 95% by 8 PM, coinciding with voters first learning of the results.

From 6 PM to 8 PM, a crucial two-hour window between Seguro's odds increase and the public announcement of results, over €5 million was traded across multiple markets.

The total volume in the main presidential market exceeded $120 million (approximately €103 million), while alternative markets accumulated nearly $10 million (approximately €8.1 million).

The puzzling aspect of how bettors accurately identified the winner two hours prior to the official announcements is clarified upon further inspection. At 6 PM, preliminary exit poll projections were circulating privately, all affirming a comfortable victory for Seguro with more than 30% of the vote.

The two candidates will compete again in a runoff election scheduled for February 8, although Polymarket will not be available for Portuguese bettors this time around.

Regulatory Actions in Portugal and Compliance Issues

The SRIJ noted that it recently became aware of Polymarket and believes the company’s operations are “illegal.”

The regulator emphasized that “the website is not authorized to offer betting in Portugal, and under national laws, betting on political events, whether national or international, is prohibited.”

Polymarket received a notice on Friday, instructing it to stop operations in Portugal within 48 hours.

However, by Monday, the site was still operational, prompting the SRIJ to involve network services to block the platform.

Portugal becomes part of a growing list of countries that have imposed restrictions on Polymarket.

The platform has also faced bans in countries such as Ukraine, Singapore, and France and is currently blocked in several others including Australia, Belgium, Germany, the UK, Iran, and North Korea.

Concerns regarding insider trading on prediction markets have heightened, particularly since there were significant bets on geopolitical events — notably after Polymarket demonstrated near-perfect accuracy in predicting President Trump’s anticipated 2024 victory.

Austin Weiler, a researcher from blockchain intelligence firm Messari, stated that preventing insider trading is “realistically feasible only on prediction markets where Know Your Customer (KYC) measures are in place.”

He added that for KYC-compliant platforms, the best practice may involve restricting users’ access to specific markets from the outset, especially regarding political or geopolitical events.

Kalshi Competes with Polymarket in the Prediction Market Space

KYC requirements can differ greatly across various established prediction markets.

Kalshi, regulated by the US Commodity Futures Trading Commission (CFTC), mandates identity verification as part of its operational framework, leading established exchanges like Coinbase to create prediction market platforms within Kalshi’s federally recognized structure.

While Polymarket is also acknowledged by the CFTC, there are significant differences in access and allowed markets, with ongoing legal debates regarding whether Polymarket’s offerings are classified as contract trading or gambling under an alternate description.

Due to regulatory challenges and lawsuits against Kalshi, Polymarket reported a 28% rise in political betting in December 2025, with over $4.3 billion wagered, compared to Kalshi’s $5.96 billion in the same timeframe.

Portugal Bans Polymarket - Messari Volume Chart