QE is a separate process from the usual act of money creation by banks making loans, it's best to consider it as an out-of-the-ordinary manual intervention by the central bank where they create new central bank money ad hoc and use that to purchase assets on the market. The normal process of money creation is banks creating new commercial bank money when making loans to individuals and companies.

https://www.bankofengland.co.uk/-/media/boe/files/quarterly-...