- Go to the contacts list and empty the filters to show all contacts
- Select all contacts
- In the dialogue that appears select 'Update company'
- Add the companies to a campaign (Pick a name that's easy to find, "Companies with contacts" for example)
- Go to companies list and with the filters:
- Use the campaign filter and select the campaign you just created
- Exclude those companies by selecting the campaign you added them in by toggling the option "Exclude selected"
- The company list will now show all companies that aren't in your campaigns, e.g companies without contacts.