What is the income of a minor to file a tax return in Wisconsin?

I suspect that you're asking what the filing requirements are for a someone who can be claimed as a dependent on someone else's return in Wisconsin.

If that's the case, then, according to the Wisconsin Department of Revenue's 2020 Wisconsin Form 1 Instructions page, you must file a return for 2020 if you can be claimed as a dependent on someone else’s return and either of the following applies:

(1) Your gross income was more than $1,100 and it included at least $351 of unearned income, or

(2) Your gross income (total unearned income and earned income) was more than –

• $11,050 if single,
• $14,280 if head of household,
• $20,470 if married filing jointly, or
• $9,720 if married filing separately.

Unearned income includes taxable interest, dividends, capital gain distributions, and taxable scholarship and fellowship grants that were not reported to you on a Form W‑2. Earned income includes wages, tips, self-employment income, and scholarship and fellowship grants that were reported to you on a Form W‑2.

If this is not what you were asking about, please rephrase your question.