Why did CA tax rate for dependent filing separating with non-earned income double after entering parent's taxable income?

[drkdhl]

For 2018, dependent on parents' return is filing 1040 and CA 540 separately. Tax owed for non-earned income is $500 until parent's taxable income from parent's 1040 is entered, then dependent's tax due is doubled. Parents are NOT including dependent's income - earned or non-earned on their return. Why is the tax so high?

[ChrystalM · Accepted solution]

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