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

Punch cards, at first. This started within a few years after WWII. The census was already being conducted using data encoded onto little cards that could quickly be run through machines and tabulated. Simple tax returns were easily encoded and processed in a similar manner, and information could be verified electronically.

Mainframe computers took over the job and enabled the IRS to perform more sophisticated analysis of tax returns for errors or potential fraud. Currently, the problem is that the old computers and software are so complicated that they can’t easily be replaced by modern systems.