If the same person is a contact at more than one of your clients, they use a single login and see a company switcher in the portal's sidebar. Everyone else sees no change.

• Each company's projects, invoices and files stay separate. Switching changes which company they're looking at.
• Their dashboard layout is saved per company.
• To give someone access to a second company, simply add them as a contact there. They get an "added to a company" email instead of a new invitation.