Invoices for discipline cases are located within the 'Finance' tab on the left-hand menu of the Whole Game System. To view these, you must be logged in under your club role rather than as an individual.
Invoices are raised via WGS on a weekly basis, so if the invoice is still not showing it has either not been raised, or has already been paid. Payments can be made for individual cases within the 'Discipline' section, providing the cases have been acknowledged.