It is possible to validate an order as a guest or by creating an account during the checkout.
If an order was placed as a guest and if an account is created with the same email address afterwards, it is possible to associate the order to said account only until the order is in status 'scored'. If the order is sent to preparation and shipment, it will no longer be possible to manually associate the previous order with this new account.
Also, if the email address of the account is incorrect, it is not possible to correct the spelling mistake. A new account needs to be created with the correct email address.