1 - As an Admin
You can create an invoice as an Admin by navigating to
'Admins' > 'Billing' > 'Invoices'
'Create an Invoice'
2 - As a Coach or Admin
You can also find them under the athlete's individual profile
'Coaches' > 'Members' > *choose the athlete* > 'Billing' > 'Invoices'
'Create New Invoice'