Child Income Tax Rules, Thresholds, and the Kiddie Tax

A child has to file a federal tax return once their income crosses IRS thresholds, and those thresholds depend on where the money came from. Under the child income tax rules for 2026, a dependent with only wages must file when earned income tops $16,100, a dependent with only investment income must file above $1,350, and any child with $400 or more in net self-employment earnings must file no matter what.¹ A separate rule called the Kiddie Tax then taxes investment income above $2,700 at the parents’ marginal rate.

Earned Income vs. Unearned Income

The IRS sorts a child’s income into two buckets, and each has its own filing trigger. Earned income is money the child worked for: wages, salaries, tips, and payment for services, whether from a W-2 job or cash for mowing lawns. Unearned income is investment return: interest, dividends, capital gains, rents, and royalties.² It also covers distributions from trusts and taxable scholarship amounts not reported on a W-2. Most children’s unearned income sits in custodial accounts set up under UTMA or UGMA.

2026 Filing Thresholds for a Dependent Child

The thresholds below apply to a child who can be claimed as a dependent on a parent’s return.¹

Earned income only: file if it exceeds $16,100, the 2026 single-filer standard deduction.
Unearned income only: file if it exceeds $1,350.
Both types: file if gross income exceeds the larger of $1,350 or earned income plus $450.
Self-employment: file if net earnings reach $400.³

The combined test trips people up. A 16-year-old who earns $4,000 at a summer job and $500 of savings interest has gross income of $4,500. The threshold is the larger of $1,350 or $4,000 plus $450, which is $4,450. Because $4,500 exceeds $4,450, the child must file. Drop the interest to $200 and gross income falls to $4,200, below the $4,450 threshold, and no return is required.

The $400 Self-Employment Rule

Freelance work, online sales, and gig-app income all count as self-employment. A child who nets $400 or more owes Social Security and Medicare tax on those earnings and must file Form 1040 with Schedule SE attached.³ Age is irrelevant. A 14-year-old who nets $500 tutoring classmates has a filing requirement.

How the Kiddie Tax Works

The Kiddie Tax prevents parents from shifting investment assets into a child’s name to have the returns taxed at the child’s low rate. It forces a portion of the child’s unearned income onto the parents’ marginal rate, which can run as high as 37%.

Who It Applies To

Three groups of children fall under the rule:⁴

Any child under 18 at year-end.
A child who is 18 at year-end, if earned income didn’t cover more than half of their support.
A full-time student ages 19 through 23, if earned income didn’t cover more than half of their support.

An 18-year-old supporting themselves with a full-time job, or a 22-year-old student paying most of their own expenses through wages, is outside the Kiddie Tax.

The Three Tiers of Unearned Income

For 2026, a child’s unearned income is taxed in layers:¹

The first $1,350 is sheltered by the child’s limited standard deduction and isn’t taxed.
The next $1,350, from $1,351 to $2,700, is taxed at the child’s own rate, usually 10%.
Anything above $2,700 is taxed at the parents’ marginal rate.

The parental-rate portion is computed on Form 8615, which is attached to the child’s Form 1040 and requires the parent’s taxable income to determine the applicable rate.⁴

Reporting a Child’s Income on the Parent’s Return

Parents can skip filing a separate return for the child and report the income on their own Form 1040 using Form 8814. The child must meet every one of these conditions:⁵

Under 19 at year-end, or under 24 if a full-time student.
The only income was interest and dividends, including capital gain distributions.
Gross income was less than $13,500 for 2026.¹
No estimated tax payments were made for the child.
No federal income tax was withheld.
The child is not filing a joint return.

If the child had any wages, withholding, or estimated payments, the election is unavailable and the child files their own return.

Folding the child’s income into the parent’s return raises the parent’s adjusted gross income, which can phase out education credits and other benefits tied to AGI. Many families end up paying less total tax by filing a separate return for the child and using Form 8615. Run both scenarios before choosing.

Filing the Return

A child’s federal return goes on Form 1040, the same form adults use.⁶ A teenager who can sign for themselves does so. For a younger child, the parent signs the child’s name followed by “By [parent’s signature], parent for minor child.” The child needs their own Social Security number or ITIN. When Form 8615 applies, the parent’s Social Security number and taxable income are required to complete it.

For the 2025 tax year, filed in 2026, the deadline is April 15, 2026.⁷ An extension pushes the return deadline to October 15, but any tax owed is still due April 15.

When It Pays to File Even If Not Required

A child whose income sits below every threshold can still benefit from filing. The most common reason is a refund. Employers withhold federal income tax based on the W-4 the employee submits, and plenty of working teenagers have tax withheld even though they owe nothing. The only way to get that money back is to file.

Filing also starts the three-year audit clock. If no return is filed, there is no statute of limitations, and the IRS can assess tax at any time.⁸ For a child with any meaningful income, locking in that three-year window is sensible even when no tax is due.

Penalties for Skipping a Required Return

The failure-to-file penalty is 5% of unpaid tax per month, up to 25%.⁹ A separate failure-to-pay penalty of 0.5% per month accrues on the balance, also capped at 25%.¹⁰ Interest compounds daily on the unpaid balance including penalties, and for early 2026 the IRS underpayment rate is 7%.¹¹

On a $300 tax bill the amounts look small, but Kiddie Tax liability that recurs year after year on a custodial account can compound quickly. The responsible party for a child’s taxes is the parent or guardian, so the penalties land on the adults.

Filing a Child’s Return Doesn’t End the Dependent Claim

A parent can still claim the child as a dependent even when the child files their own return. The two decisions are separate. Dependent status requires the child to meet tests for relationship, age, residency, support, and joint-return status.⁶ The age test requires the child to be under 19 at year-end, under 24 if a full-time student, or any age if permanently and totally disabled. Claiming the dependent opens the door to the Child Tax Credit, the Earned Income Tax Credit, and the Child and Dependent Care Credit.¹²

The trade-off is that a dependent’s standard deduction is capped at the greater of $1,350 or earned income plus $450 rather than the full $16,100.¹ That limited deduction is why a child with only investment income has to file above $1,350: there’s only $1,350 of shelter, so everything past that becomes taxable.

State Returns Follow Different Rules

Federal thresholds don’t govern state filing. Most states with an income tax set their own thresholds for dependents, and those figures are often lower than the federal ones. Some states track the federal rules; others tie their thresholds to a state personal exemption. A child who owes no federal return may still owe a state return, particularly with investment income. Check the state tax agency where the child lives for the specific numbers.

1
Internal Revenue Service. Revenue Procedure 2025-32, 2026 Adjusted Items
2
Internal Revenue Service. Instructions for Form 8615 (2025)
3
Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
4
Internal Revenue Service. Topic No. 553, Tax on a Child’s Investment and Other Unearned Income (Kiddie Tax)
5
Internal Revenue Service. Instructions for Form 8814, Parents’ Election To Report Child’s Interest and Dividends
6
Internal Revenue Service. Publication 501 (2025), Dependents, Standard Deduction, and Filing Information
7
Internal Revenue Service. IRS Announces First Day of 2026 Filing Season; Online Tools and Resources Help with Tax Filing
8
Internal Revenue Service. Time IRS Can Assess Tax
9
Internal Revenue Service. Failure to File Penalty
10
Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges
11
Internal Revenue Service. Quarterly Interest Rates
12
Internal Revenue Service. Dependents