See also the official documentation:
Help Center > Group Owners Manual > Inviting people to join a group
Owners and moderators who have been given permission (See Members, Role, Moderator Permissions) can invite people to join your group as members using the potential member's email address.
This works with all groups, including basic (free) groups. Normally though, you would use "direct add" rather than invite with Premium or Enterprise groups.
- Go to Admin, Invite.
- You can customize parts of the message to improve acceptance rate.
- You can include a notice, if you wish. For the type Invite, you can set up as many notices as you'd like, or none. If you have at least one, it will be in the Notices box on the Invite page in the Customize Message area and you can choose to insert it into the standard invitation. If you have several, you can choose which one of them to use.
- You can also create a Welcome notice that includes your terms of service or other info you wish new members to read. See the wiki on Notices.
- Type in the email addresses of people you want to invite. Or upload a list. But it needs to be in plain text. It can't be UTF-16LE. It must be UTF-8 (it works both with or without faux byte order mark).
See the page about the 20 member limit of invitations in a 24 hour period. This applies no matter which plan you are on - free, premium or enterprise.
- Send invitations.
- You can track who has accepted on the Sent Invitation button on the Invite page.
- You can Cancel/Remove Invite - this just removes the email address from this list. It doesn't remove their membership in your group if they have accepted. Or you can send again to prod them to reply!
NOTE: People you invite will be automatically added to your group when they accept the invitation, even if you have a restricted group.