If you have not yet filed your tax return,sign into your Online account and click the orange button that says "Take me to my return then go to the Personal Info tab and select edit next to your name and make the correction to your last name.
If you have already filed your tax return you first need to wait and see if your return is accepted or rejected.If rejected you can go back and make the correction following the steps above. If accepted you will not need to do anything further just be sure the information is correct on next year's return.
Depending on the misspelling of the last name, your tax return may be fine. The IRS will verify the Beginning letters of your last name and your Social Security Number with what what you Social Security Card is showing.