The Tax Cuts and Jobs Act (TCJA) made substantial changes to the Kiddie Tax in 2018 through 2025. Instead of using the parent’s highest marginal rate, the Kiddie Tax is now determined by the tax brackets and rates for trusts and estates on the federal return.
California does not conform, the Kiddie Tax rate is equal to the parent’s highest marginal tax rate. This is why entering the parents income will change the amount of tax that is due. Follow this link for more information on the Kiddy Tax. https://ttlc.intuit.com/replies/3301446
