The Facts About Income Tax Millions faithfully file their 1040 forms each April. But some things about federal income taxes may surprise you. Share | Related Content Comparing Investments This calculator compares the net gain of a taxable investment versus a tax-favored one. What Do Your Taxes Pay For? Here's a breakdown of how the federal government spends your tax money. Tax Freedom Day Assess how many days you'll work to pay your federal tax liability.