Invoice another DesignFiles admin account

I’ve ran into a few scenarios where I need to invoice another designer/user of DesignFiles to pay me back for various services or furnishings. Currently, the system will not allow the use of their same email created for their admin account. Instead, a secondary email has to be used. This is not always possible if they only have one email. Please update this feature so another designer/user account can be invoiced as a “client” without needing a separate email login.