To help pay for the war, the federal government increased corporate and personal income taxes. When income taxes were introduced, only the wealthiest Americans were taxed. With the war, tax rates were increased and the wage level at which people started to pay was lowered. This, and the increase in employment in war industries, caused many more people to have to file. In 1939 fewer than 8 million people filed individual income tax returns. In 1945 nearly 50 million filed.
Factoid: Propaganda films starring popular cartoon characters such as Donald Duck emphasized the need to pay taxes.