There are two ways of inviting a business to the event; using the quick search for known contacts and via the search screen to work through a list.
The Search screen for most CRMs will display the Contact screen. Click Event. Fig.1
The default filters on the Event search screen are Fig.2:
Click Not Invited Fig.3 (1) to set the filter to 'Not Invited' and '1 per company'. The number of businesses will be displayed with no contacts that have been invited Fig.3 (2). Click the first name to work through the list. Fig.3 (3)