The Kiddie Tax for US Kids in Canadian Families: Whose Rate, Which Income, and How It Meets Canadian Attribution

The kiddie tax is the US rule that stops parents from parking investments in a child's name to use the child's low bracket: a child's unearned income above an indexed threshold (about $2,700 for current years) is taxed at the parent's marginal rate, computed on Form 8615 attached to the child's return. The rule follows the child's US-person status, not the family's address — a US-citizen teenager in Mississauga with a dividend portfolio is inside it. Canada approaches the same policy problem with different tools pointed at different taxpayers: the attribution rules tax a minor's interest and dividend income from parental gifts to the parent directly, and the tax on split income (TOSI) taxes private-company dividends to a minor at the top rate on the child's own return. When a family straddles both systems, the same dollars can be taxed to different people at different rates in the two countries — which breaks the foreign tax credit mechanics that normally prevent double taxation, because credits require the same person to be taxed on the same income.

Key takeaways

• Who is caught: a child under 18 — or under 24 if a full-time student whose earned income doesn't exceed half their support — with unearned income above the threshold and at least one living parent. US citizenship makes a child in Canada a US taxpayer with a filing obligation once income thresholds are met.
• What is unearned: interest, dividends, capital gains, rents, royalties — including everything a Canadian ITF account or a gifted portfolio throws off, and including income Canada attributes away from the child.
• Whose rate: the parent's US marginal rate. Form 8615 needs the parent's taxable income; where parents file separately, the higher-income parent's; where the parent is a nonresident alien with no US return, the computation runs on the information available and professional judgment fills the statutory gaps — one of several places the form assumes a domestic family.
• The mismatch with Canada: Canada may tax the parent (attribution) or the child at top rate (TOSI) while the US taxes the child at the parent's rate. Foreign tax credits work person by person, so Canadian tax paid by the parent does not credit against US tax owed by the child on the same income.
• PFIC income stacks on top: the Canadian mutual funds typically inside a child's account are PFICs; excess distributions carry their own regime and then feed the kiddie tax computation.
• Elections: in wholly domestic cases parents can sometimes report a child's income on their own return (Form 8814); the eligibility conditions frequently fail for cross-border families (foreign tax credits and PFIC items on the child's side make 8814 unavailable or unwise).

Designing around it

The kiddie tax cannot be planned away by moving income to the child — that is the point of it — but a cross-border family can control the character and location of the child's assets. Unrealized growth doesn't trigger it: broad-market US-listed ETFs bought and held in the child's name generate modest distributions and defer gains until the child ages out of the regime. Canadian mutual funds are the worst container (PFIC plus kiddie tax); a formal trust is not an escape (a Canadian trust with a US child beneficiary adds Form 3520 and throwback to the same problem); and an RESP has its own US character issues when the subscriber or beneficiary is a US person. The clean designs are boring: growth-oriented, US-compliant holdings, distributions under the threshold, and the family's income-splitting done through Canadian-side tools that don't put unearned income on a US child's return.

Worked example

A Waterloo couple — Canadian father, US-citizen mother — hold $120,000 in an account for their 15-year-old daughter, a US citizen. The account, funded by the father, holds Canadian dividend funds paying $4,800 a year plus $2,000 of realized gains. Canada: the $4,800 of income attributes to the father and is taxed to him; the gains are the daughter's, under her basic personal amount — no Canadian tax for her. US: the daughter has $6,800 of unearned income; roughly $4,100 above the threshold is taxed at her mother's marginal rate (the parent whose return the form draws on here), and the funds are PFICs, so the computation runs through Form 8621 first. The father's Canadian tax cannot credit against the daughter's US bill — different taxpayers. The fix going forward: swap the Canadian funds for US-listed index ETFs (no PFIC), keep annual distributions near $2,000, and let gains ride until she is 24 — after which her own bracket, in both countries, applies.

Official sources

The IRS explains that a child's unearned income above an annual threshold may be taxed at the parent's marginal rate rather than the child's rate, computed on Form 8615, where the child is under 18 (or under 24 for certain students) and has at least one living parent. — Internal Revenue Service, Topic No. 553, Tax on a Child's Investment and Other Unearned Income (Kiddie Tax), https://www.irs.gov/taxtopics/tc553

The CRA explains the tax on split income, under which certain income of a child under 18 — including taxable dividends from private corporations, directly or through a trust — is taxed at the highest marginal rate on the child's return. — Canada Revenue Agency, Tax on split income (line 40424), https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/line-40424-federal-tax-on-split-income.html

Practitioner note

The kiddie tax is a domestic anti-avoidance rule that lands awkwardly on families who never planned any avoidance — a Canadian grandparent's generosity becomes a US rate problem for a teenager. The design rule we apply: nothing that distributes heavily, nothing that is a PFIC, and nothing above the threshold until the child ages out; income splitting for a cross-border family happens on the Canadian side or not at all.

See also: Browse every cross-border tax topic guide, organized by situation.

Next step

Fairlight prepares the child's US return with Forms 8615 and 8621, the parent-rate computation in mixed-status families, and the portfolio redesign that keeps the next years under the threshold. See cross-border pricing or book a call.