If you received a 1099, then the IRS also received a copy of it. If you choose not to report your 1099 earnings, then the IRS will send you a CP2000 notice, which is referred to as a "matching notice." This notice lets you know that you had unreported income, and it assesses the taxes you were supposed to pay, as well as any penalties or interest for not paying them on time, if applicable. It's better to report the income on your tax return because that way you can also claim deductions that might limit your tax burden. Plus, you avoid getting a notice.