how did the IRS or any other revenue agency audit dozens of millions of paper tax returns every year before computers were common?

Question

How did they verify if someone committed fraud or tax evasion in the 1950s for example?

In: 19

Answer 1

They employed lots of people. The IRS building in Washington DC is vast inside, and barely occupied today (I worked there for a while). It would have housed 1000s of clerks.