This is the Department that the Payer Type is linked to. A single Payer Type can be linked to several different Departments (e.g. if the HSE is your Payer Type there will be a huge number of linked Departments) so you need to specify which Department (name and address) is to receive the invoice.
These Departments can be configured on the system as per the requirements of your organisation, and those listed below are simply examples:
§ CCA6 (or LHO6)
§ HEP C
§ LHO7/HCP Over 65
§ LHO8
§ LMSU