If you forgot to include a $1,000 Form 1099, you should Amend your Tax Return once it has been fully processed and you have received your refund. You can click here for instructions on Amending your tax return: How to Change a Tax Return You Already Filed.
The IRS will correct it eventually, but it usually takes them an average of 1-2 years to catch the error. This means that they will add interest and/or penalties from that time period.
It is definitely best to be proactive and Amend your return by April 15, 2019 to avoid any interest and penalties.
