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 Capital Gains Tax Estimator Use this calculator to estimate your capital gains tax. What Is a 1035 Exchange? 1035 exchanges provide a way to trade-in an annuity contract or life insurance policy without triggering a tax liability. Federal Income Tax Use this calculator to estimate your income tax liability along with average and marginal tax rates.