No, it is not illegal to invest under 18. What stops a minor from investing directly is contract law, not criminal law: people under the age of majority (18 in most states) lack the legal capacity to enter binding agreements, and brokerages, banks, and fund companies won’t open accounts for someone who could void the contract at any time. The workaround is straightforward. An adult opens an account structured to hold and grow assets on the minor’s behalf, and there are several types to choose from.
Why a Minor Can’t Just Open a Brokerage Account
The barrier is contract voidability. A minor who signs an agreement can cancel it at any point before reaching the age of majority, and for a reasonable time afterward. Financial institutions rely on enforceable contracts with their customers, so they refuse to open accounts for anyone who could walk away from the relationship on a whim. No statute makes it a criminal offense for a teenager to try to invest. The restriction comes from a long-standing legal principle meant to protect young people from being locked into deals they don’t fully understand.
In practice, a 16-year-old can’t sign up for a brokerage account, buy shares of stock, or enter a futures contract in their own name. The adults around that teenager, however, have several well-established ways to invest for them, and some of those structures carry real tax advantages.
Accounts an Adult Can Open for a Minor
UGMA and UTMA Custodial Accounts
The most common route is a custodial account set up under the Uniform Gifts to Minors Act (UGMA) or the Uniform Transfers to Minors Act (UTMA). A parent or grandparent opens the account as custodian, makes the investment decisions, and manages the money until the child reaches the termination age set by state law. UTMA is available in every state except South Carolina, which uses UGMA only.
The main difference is what the account can hold. UGMA accounts are limited to financial assets: cash, stocks, bonds, and mutual funds. UTMA accounts accept a broader range of property, including real estate, patents, and fine art, in addition to all the financial instruments a UGMA can hold. For a family buying index funds for a child, the distinction rarely matters.
Once assets go into either account, they belong to the child irrevocably. You can’t take the money back, change your mind, or redirect it to another beneficiary. The custodian controls the investments but has a fiduciary duty to manage them for the child’s benefit, and earnings are reported under the child’s Social Security number.
Custodial Roth IRA
If the minor has earned income from a job or self-employment, a custodial Roth IRA is one of the more powerful tools available. Money goes in after tax, grows tax-free, and comes out tax-free in retirement. Starting a Roth at 14 or 15 gives compounding decades of extra runway.
The contribution limit for 2026 is $7,500 or the child’s total earned income for the year, whichever is smaller. A teenager who earns $3,000 mowing lawns can contribute up to $3,000, not a penny more. The cash doesn’t have to come from the child’s own account; a parent can fund the contribution as long as the child actually earned at least that much during the year.
What counts as earned income matters. Wages from a W-2 job qualify, and so does net self-employment income from babysitting, tutoring, freelance work, or a small lawn care business. Allowances, birthday money, and investment income do not. The IRS defines earned income as wages, salaries, tips, and net self-employment earnings.
The parent or guardian manages the Roth IRA until the child reaches the age of majority, at which point it converts to a standard Roth IRA in the child’s name. Contributions (but not earnings) can be withdrawn at any time without tax or penalty, which gives the child some flexibility before retirement.
529 College Savings Plan
A 529 plan works differently in one important way: the account owner keeps control of the money indefinitely. You can change the beneficiary to another family member, and the child never gains an automatic right to take over the account. For families worried about a young adult suddenly having unrestricted access to a large balance, that control is a real advantage.
Earnings grow tax-free, and withdrawals are tax-free when used for qualified education expenses: tuition, room and board, books, and required supplies at eligible institutions. The tax-free treatment extends to K-12 tuition up to $10,000 per year and up to $10,000 lifetime for student loan repayment. Withdrawals for anything else trigger income tax on the earnings portion plus a 10% penalty.
The SECURE 2.0 Act added an escape hatch starting in 2024: unused 529 funds can be rolled into a Roth IRA for the beneficiary, subject to three conditions. The 529 must have been open for at least 15 years, the annual rollover can’t exceed the Roth IRA contribution limit for that year ($7,500 in 2026), and the lifetime cap is $35,000 per beneficiary.
The Kiddie Tax on Investment Earnings
Any investment held in a child’s name, whether in a custodial brokerage account, UGMA, or UTMA, generates taxable income under special rules. The IRS applies what’s informally called the “kiddie tax” to a child’s unearned income (interest, dividends, and capital gains). For 2026, the tiers are:
- First $1,350: tax-free.
- Next $1,350: taxed at the child’s own rate (typically 10%).
- Above $2,700: taxed at the parent’s marginal rate.
That third tier is the one that stings. If a custodial account generates $10,000 in capital gains and the parent is in the 32% bracket, the portion above $2,700 gets taxed at 32% rather than the 10% rate the child would otherwise pay. The rule exists specifically to stop parents from sheltering investment income in a child’s name to reach lower brackets.
The kiddie tax also lasts longer than people expect. It applies to children under 18, to 18-year-olds whose earned income doesn’t cover more than half their own support, and to full-time students aged 19 through 23 whose earned income doesn’t cover more than half their support. A college junior with a large custodial account and a part-time campus job is almost certainly still subject to it.
What Happens When the Child Reaches the Termination Age
The termination age varies by state, and this catches families off guard. Most states set the default at 21, though a number allow termination as early as 18 and a few permit extensions to 25 or older. When the child hits that age, the custodian’s authority ends. Assets and records transfer to the now-adult beneficiary, with no conditions and no strings.
The former minor then has unrestricted control. There is no mechanism to delay the transfer, impose conditions, or hold back a portion of the funds. The money can go to college tuition, a car, a trip, or something you’d rather not think about. That complete loss of control is the single biggest drawback of custodial accounts. If it concerns you, and for large balances it probably should, a 529 plan or a formal trust gives the adult more say over how and when the money gets used. A trust costs more to set up but lets you attach conditions such as reaching age 25 or graduating college before the beneficiary gets access.
Emancipated Minors
Minors who have been legally emancipated, through a court order, marriage, or military service depending on the state, gain many of the legal rights of adults, including the ability to manage their own earnings. In theory, an emancipated minor has the capacity to enter contracts. In practice, most brokerages still require account holders to be 18, and some states retain restrictions on certain contracts even for emancipated minors. If this describes your situation, contact the brokerage directly and be prepared to provide a copy of the emancipation order. Don’t assume the standard online application will work.