About the Kiddie Tax Calculator
The Kiddie Tax Calculator estimates the federal tax owed on a child's unearned investment income, such as dividends, interest, and capital gains, under the rules designed to stop parents from shifting investment income into a child's lower bracket to reduce their own tax bill. You enter the child's total unearned income and the parent's marginal tax rate, and the calculator applies the tiered structure that taxes the income at three different levels depending on how much there is.
How It Works
The first slice of unearned income is treated as tax-free, covered by the dependent's standard deduction. The next slice is taxed at the child's own flat 10% rate. Any unearned income above that combined threshold is taxed at the parent's marginal rate instead of the child's, which is the core mechanism that removes the incentive to shift income to a child in a lower bracket.
Formula & Methodology
With $5,000 of unearned income and a 32% parent marginal rate: $1,350 is untaxed, the next $1,350 (up to $2,700) is taxed at 10% for $135, and the remaining $2,300 above $2,700 is taxed at 32% for $736, giving a total kiddie tax of $871. If unearned income were only $2,000, none of it would reach the parent-rate tier, since $2,000 is below the $2,700 combined threshold, so only the $650 falling in the 10% band would be taxed, at $65.
Examples
$5,000 in unearned income
A child with $5,000 in dividends and interest, and a parent in the 32% bracket, owes an estimated $871: $135 from the 10% child-rate tier plus $736 taxed at the parent's 32% rate on the $2,300 above the combined threshold.
$2,000 in unearned income
A child with only $2,000 in unearned income stays entirely within the untaxed and child-rate tiers, producing an estimated $65 in kiddie tax regardless of the parent's marginal rate, since none of it reaches the parent-rate threshold.
Advantages
- Breaks the kiddie tax's tiered structure into its three components so you can see exactly how much of a child's investment income lands in each tax tier.
- Shows how sensitive the total tax is to the parent's marginal rate once income crosses the $2,700 combined threshold, since that tier scales directly with the parent's bracket.
- Helps illustrate why the kiddie tax rules limit the tax benefit of shifting large amounts of investment income to a child's name.
Common Mistakes
- Assuming kiddie tax applies to a child's wages from a job; it applies only to unearned investment income, not earned income, which is taxed at the child's own regular rates regardless of amount.
- Forgetting that the parent's marginal rate, not the child's, governs the largest tier once unearned income exceeds the combined threshold, which can make a child's investment income surprisingly expensive to hold.
- Using outdated threshold figures; the $1,350 tiers used here reflect approximate 2025 amounts and are adjusted for inflation most years, so they should be checked against the current tax year.
Edge Cases to Watch For
- If unearned income is at or below $1,350, both taxable tiers compute to zero, so the estimated kiddie tax is $0 entirely.
- If unearned income falls between $1,350 and $2,700, only the 10% child-rate tier applies; the parent-rate portion is zero because it is floored at zero once income does not exceed $2,700.
- The calculator estimates the resulting tax liability only; it does not model the choice between reporting the income on the child's own return (Form 8615) versus the parent electing to include it on their own return (Form 8814), which are two different filing mechanisms for the same underlying tax.
Common Use Cases
- Parents deciding how much investment income to let accumulate in a custodial account for a child.
- A family weighing whether to gift appreciating assets to a child now versus holding them until the child reaches adulthood.
- Tax preparers illustrating to clients why large unearned income amounts in a child's name do not escape the parent's tax bracket.