If you have answered "Yes" to the question about Tax On Split Income (TOSI) in the Info section of your TurboTax Online return in error, you can change this to "No", by returning to My Info > Get Started and proceed to the page that asks you "Taxpayer, did you, your spouse/partner, or dependent receive split income? (This does not apply to pension income splitting)." Change this answer to "No" and the Error should go away. Also check the spouse's return to see it is answered correctly as well.