A primary account relationship is a feature that allows you to link a contact to a single account as its primary account. A primary account relationship is required on a contact regardless of the page layout settings or the contact to multiple accounts feature. This means that you cannot remove the primary account from a contact, but you can change it to another account. You can also add secondary accounts to a contact if you have enabled the contact to multiple accounts feature. Reference: https://help.salesforce.com/s/articleView?id=sf.contacts_multiple_accounts.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.contacts_fields.htm&type=5