What percentage of that is automated audit, and what percentage is manual audit? Nowaday my country is mostly sane with tax filings, but in the weird time between the 90s and the 2010s, we had an uptick in "fraud" by low-income earners. This was caused by inconsistencies between filed data and the data the IRS equivalent had, but i guarantee you no effort was put into thsi (except secreterial manpower for the hotline/mail), that was just automated system ringing.

In fact my first college side-job was exactly that, responding to taxpayers who were "caught" by the automated system and needed a payment delay.