What do the lesser-known but important services like IAAS, IDAS, IIS and ICAS actually do?

These are the 'invisible' services that keep the Republic financially honest and communicatively coherent. IAAS audits the entire government on behalf of the CAG; IDAS keeps the Armed Forces' books and pays soldiers on time; ICAS runs the Union's payments and accounts under the Controller General of Accounts; IIS is the communication arm — DD News, AIR, PIB and government messaging. None of them rule districts, but together they decide whether public money is honestly spent and honestly explained.