Credit Suisse said its chair Sir António Horta-Osório breached local quarantine rules in Switzerland when he spent three days in the country at the start of this month.
The banker arrived in the country from London on 28 November, faced with a 10-day quarantine as a result of the Covid-19 Omicron variant. He flew out of Switzerland four days later on 1 December, first reported by Swiss newspaper Blick.