What happens when you discover you made a mistake on your 2016 return that you just filed?

First, don’t panic, and second, don’t ignore the error.

Do file an amended return if you need to change your tax filing status or dependency exemptions, or you overlooked available deductions or credits.
Don’t file an amended return to correct simple mathematical miscalculations or forms you forgot to attach. The IRS corrects those types of mistakes and sends you a notice.
Do file the amended return as soon as you discover your error.  However, if the change will result in a larger refund, wait until you receive the refund shown on your original return.
Don’t wait too long. Amended returns must generally be filed within three years from the date you filed your original return.
Call us if you discover an error or missing information on a return you already filed.