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 Federal Income Tax Use this calculator to estimate your income tax liability along with average and marginal tax rates. What Do Your Taxes Pay For? Here's a breakdown of how the federal government spends your tax money. Home Mortgage Deduction Use this calculator to assess the potential benefits of a home mortgage deduction.