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 Making Your Tax Bracket Work Have you explored all your options when it comes to managing your taxable income? Red Flags for Tax Auditors Here are six flags that may make your tax return prime for an IRS audit. Comparing Investments This calculator compares the net gain of a taxable investment versus a tax-favored one.