If your grandson didn't live or work in Wisconsin, he generally shouldn't owe any tax to the state. There are a couple of places in TurboTax that would generate a state tax return. If you haven't filed the return yet, check these areas:
1. On the My Info tab, the last section asks if you earned income in any other state. Make sure the answer here is No, I didn't make money in any other states.
2. You said the employer didn't take any Wisconsin tax. On the W-2 input screen, make sure Wisconsin wasn't added as a state under the State tax section.
3. In the State Tax return section, delete the Wisconsin return.
If you've already filed the returns, you'll need to amend the Wisconsin return to reverse the income and eliminate any tax owed. Follow the instructions in this help article, How to amend my state return in TurboTax, to create the amended return.
