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 the New Tax Bill Means for You What does the Tax Reform and Jobs Act mean for you? Federal Income Tax Use this calculator to estimate your income tax liability along with average and marginal tax rates.