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 Making Your Tax Bracket Work Have you explored all your options when it comes to managing your taxable income? Understanding Marginal Income Tax Brackets An inside look at how marginal income tax brackets work. Comparing Investments This calculator compares the net gain of a taxable investment versus a tax-favored one.