When adding or editing a sub-account, you may run into a message saying that the email address already exists:

This means that the email address you are attempting to use for the account has already been used for another InventoryLab account or as a sub-user for another account.

At this time, an email address can only be used once in InventoryLab's system. To work around this, you can create a new email address for the sub-user to log in with or see if they have another email address already available that they'd like to use.