Tax Reform: Before and After Full Size Version Share | Related Content The Facts About Income Tax Millions faithfully file their 1040 forms each April. But some things about federal income taxes may surprise you. Do You Owe The AMT? If you want to avoid potential surprises at tax time, it may make sense to know where you stand when it comes to the AMT. Federal Income Tax Use this calculator to estimate your income tax liability along with average and marginal tax rates.