A "tenant invoice" shouldn't be confused with a "rental invoice" as they work differently and are used for different purposes.
There should never be any need to manually add an invoice for rent owing only.
The only exception might to send an invoice at the beginning of a tenancy along with other monies due such as a tenancy deposit. Or, you might send a tenant invoice containing rent at the end of a tenancy if other amounts are also due (such as damage).
A tenant invoice is used for tracking other amounts due throughout a tenancy for example:
requesting payment for damage
requesting payment after lost key
any other request which is not solely rent
A tenant invoice can also act as a credit note (see in a moment)