I did not participate in an employer 401K in 2018. The IRA Contribution Worksheet has checked a box that indicates I was. How do I change this?

[HelenaC]

You can't change the box. The IRA Contribution Worksheet gets the information from your W-2. If your W-2, Box 13 Retirement Plan box is checked, it doesn't mean you "participated" in your employer's retirement plan, it means your employer has a retirement plan "available" to employees.