Within Teamwork, you can create external companies to group certain users on your site.
Go to the People area of your site and select the Companies subsection.
Adding a company
To create a new company on your site, click the Add Company button in the top right of the companies area.
You will then be able to add the details for the new company, including any address details in the Address tab.
You can add public notes about the company in the Profile tab, and private notes in the Notes tab (they will only be visible to people in the owner company).
Editing a company
You can click the name of any existing companies in the list to view the company details page.
To the top right of the company profile, you will see an Edit button which will allow you to edit the details in the same view as when creating a company.
For more information, see: Adding or Updating a User's Company