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. Tax Rules When Selling Your Home The tax rules governing profits you realize from the sale of your home have changed in recent years. Tax Freedom Day Assess how many days you'll work to pay your federal tax liability.