9. Signature required
Sign and date your return. The IRS won't process it if it's missing a John Hancock, and that means on e-filed returns, too. Taxpayers filing electronically must sign the return electronically using a personal identification number, or PIN. To verify your identity, you'll have to provide the PIN you used last year or your adjusted gross income from your previous year's tax return. Your tax software should walk you through the e-signature process, but if you're still mailing your return, don't be in such a hurry that you stuff your 1040 in the preaddressed IRS envelope without signing it. And if it's a joint filing, you and your spouse both must sign.