It is an interesting day for Poland based online broker XTB (WSE:XTB), as the company announced its inclusion in the STOXX Europe 600 index, effective September 21. The STOXX Europe 600 Index is derived from the STOXX Europe Total Market Index (TMI). It tracks the 600 largest companies listed in 17 European countries.

However XTB shares have largely ignored the positive news, which will likely encourage more retail and institutional investors to pick up more XTB shares as it joins the index.

The reason – an announcement from Polish financial regulator Komisja Nadzoru Finansowego (KNF), that it is upholding an earlier announced PLN 20 million (USD $5.4 million) fine against XTB.

The KNF announced back in March that it was hitting XTB with the fairly significant fine, for (among other things) providing clients or potential clients with unreliable and misleading information, and client suitability testing issues.

As of the time of writing XTB shares were down 5.1% today (Wednesday) to PLN 173.50. We would note that XTB shares have more than doubled (+136%) year-to-date in 2026, as the company has continued to produce strong results.

Back to the STOXX Europe 600 index inclusion, Omar Arnaout, CEO of XTB said,

“Inclusion in the STOXX Europe 600 is a significant milestone for XTB. We are proud to join a cohort of influential companies that define the strength of the European market. Our ambition is to be a leader in the investment industry, and this recognition reinforces our commitment to driving innovation and growth across the continent.”