What are you "fixing" in your tax return? Are you adding unearned income, such as investment income? Unearned income is basically any income that wasn't from working. If your total unearned income is $2,200 or less you do not have to fill out Form 8615. If the changes you are making put your total unearned income over $2,200, then you have to fill out Form 8615. Your unearned income over $2,200 is taxed at your parents' tax rate. Obviously, in order to calculate the tax at your parents' rate, TurboTax needs information from your parents' tax return.

The tax at your parents' tax rate is commonly called "kiddie tax" from the days when it only applied to children under 14. The age limit has been raised to where it can apply to adult children who are still in school, but the name has stuck.

If you have unearned income (income not earned from working, which includes investments and unemployment compensation) then you are subject to the "Kiddie Tax", and your tax rate is based on your parent's tax information.

https://ttlc.intuit.com/community/income/help/what-is-the-kiddie-tax/00/25913

This has always been true but it is affecting more people than usual this year because many young people got enhanced unemployment benefits for the first time, and if you got UEC but were under age 24 and partly supported by your parents, you can be subject to this tax.