The news was announced on Friday by Dorota Niedziela, the head of the party's commission responsible for organising the primaries.
Two prominent KO politicians, Warsaw Mayor Rafal Trzaskowski and Foreign Minister Radoslaw Sikorski, will face off in next Friday's vote, which will be carried out through a secure text messaging system and will be anonymous.
According to Niedziela, the results will be published on the next day.
The victorious candidate will present the programme for his five-year presidency on December 7.
Poland will elect its next head of state in May 2025. The incumbent, Andrzej Duda, has been in office since 2015. In 2020, he won his second term against Trzaskowski. (PAP)
jd/jch