Illya Gerasymchuk
Entrepreneur / Engineer
also note that it's not just commercial banks that have accounts at the central bank. it varies by jurisdiction, but other entities also have accounts at the central bank for example, in the US the Treasury has an account at the Fed - the Treasury General Account (TGA)
if it's the central bank buying assets from other banks, such as in QE - then the central bank also creates the deposit "out of thin air", thus effectively paying for the assets to the commercial bank with a newly created deposit into their reserve account. base money increases