If you’re no longer financially connected to a partner, you can contact the credit referencing agencies and ask for a ‘financial disassociation’ to be created on your file. This means that any link to that person will be permanently removed from your file and their spending behaviour will no longer impact your credit score.
To get a financial disassociation, you’ll need to make a formal request with each of the major credit referencing agencies. You’ll be asked to list addresses you shared and declare that you no longer share any financial ties. This includes bank accounts and joint credit agreements.