Can a user invite anyone a group?

I'd like to add to Amanda's answer where she indicated only users that have been granted admin permission can add users. It's useful to understand the logic for determining who or how many individuals can have admin control. We currently are experiencing a coronavirus pandemic. It's possible that a designated Basecamp admin could be unavailable to maintain a team or project. In that case, it would be advised to have another backup admin. Bear in mind, any admin or backup should be aware of the logical foundation for allowing or rejecting any request for a member being added to their team/project: 1. Can the new member beneficially contribute to the team as a user? 2. Is the material covered in the team/project of any sensitive nature, which could exclude the backup admin performing that role? 3. Has the admin shared with their backup the restrictions for any user additions? For instance, if sensitive HR, payroll, or financial data appears in the project folder, what user acceptance criteria will be documented for the backup admin to manage any future user access requests? Note that an admin can permit a user to have access rights to project content, even if the user is associated with another company. This is good news if a project is designed to be managed by a service provider, providing more transparency in their activities on behalf of their client that they include as a user.

Only if they are given those permissions