My 14-Year-Old's Brokerage Account Owed the IRS $1,240

Sunday afternoon, Mar 8, 2:10 pm, dining table covered in W-2s and a laptop running tax software, my daughter doing homework across from me with headphones on, and I was clicking thru our return at the speed of a man who has done this eleven times. Then the screen stopped me. A single line under her name, on Form 8615, reading additional tax on your child's unearned income, and a number after it: $1,240. I read it aloud before I could stop myself. She pulled one headphone off and asked if she was in trouble, and honestly, at that moment, neither of us knew.

The account behind that line was supposed to be the good part of my financial life. Since 2018, when Amara was six, $150 a month had gone into a custodial brokerage holding one broad S&P 500 index fund, automatic, boring, the cleanest thing I have ever built with money. Eight years of statements went into a folder labeled with her name. The balance was $24,800 by last August, and I had told myself for eight years that this account was the lesson. It was. Just not the one I planned.

The $1,240 came from one withdrawal I made without thinking awfully hard. That is the part I keep re-explaining to other parents at pickup, and the part I will explain to you now, because the tax code has a trapdoor in it that only opens under fourteen-year-olds.

$150 a month since she was six

I opened the UTMA the week she lost her first tooth, which is a sentimental sentence for what was honestly twenty minutes on a brokerage website in February 2018. A hundred and fifty dollars a month, timed to my payday, into a total-market index fund, no trading, no drama, dividends reinvesting themselves for eight years. The statements were the only mail she ever asked about, and from age eight she could tell you approximately what the balance was, because we made a small ritual of the December one with hot chocolate. Contributions totaled $14,400 over ninety-six months. Compounding and one awfully good decade did the other $10,400, and I mention that split cuz it taught her more about patience than any lecture I gave.

the August sale for the school deposit

In August 2025 her new school wanted a $6,800 deposit, there was a robotics competition in Houston with a $2,900 travel bill attached, and rather than disturb our emergency fund I sold $12,400 of her shares, which at the time felt like the account doing exactly its job. I picked lots with my eyes half on a football game, clicked confirm, and moved the proceeds to a high-yield savings account at 4.2 percent while the invoices caught up, then paid both bills in September. The gain on those lots, it turned out, was $7,300, cuz everythin snagged before 2023 had approximately doubled. Not one dollar of that math entered my head in August. In August it was just the school account paying for school, the way the folder invariably implied it would.

form 8615, courtesy of a stranger

At 1 am on a Tuesday in early March, three days into tryin to understand that line, I found the answer on a forum, posted by a stranger with a screen name from a band nobody remembers. Section 1(g) of the tax code, the kiddie tax, applied to a minor's unearned income above a threshold, and it existed to stop parents from sheltering income in their children. The stranger's post was four sentences long and clearer than every official page I had read that evening. Below it, a reply from some other parent in some other state: I wish someone had told me at the account opening. I sat with that sentence for a while. Nobody tells you at the account opening. The brokerage certainly did not, in 2018 or in August, and I have gone back thru every welcome email to be sure.

the kiddie tax arithmetic

The mechanics are simple once someone shows you, which is the insult of it. For 2025, a child's first $1,350 of unearned income is covered, the next $1,350 is taxed at the child's own rate, which for Amara meant 10 percent, and everything above $2,700 is taxed at the parents' marginal rate. Her $7,300 gain broke into those three slices: $1,350 free, $135 of tax on the middle band, and $4,600 of gain taxed at our 24 percent bracket, which is $1,104. Total, $1,239, which the software rounded to the $1,240 that stopped my Sunday. Under an adult's long-term capital gains tax rates, the same sale would have owed under $900, but children do not get the discounted rate on their top slice of unearned income, and that single design choice is what turned a routine school sale into a four-figure bill. The sum of her gains above that threshold got taxed as if I had earned it, cuz in the law's eyes that is more or less what happened, and the law is not entirely wrong about families like mine.

what nobody says at the account opening

Here is the guidance I now repeat like a missionary. A custodial account is a lovely engine and a booby-trapped one, and the trap is calendar-based, so you can plan around it if yknow it exists. Hold past mid-August of her eighteenth year, and the whole problem evaporates, because after that the gains are taxed at her own starving-student rates. Sell earlier, and you can slice the gain across tax years, keeping each year under $2,700, which would have turned our $1,240 into approximately $135 spread over three Augusts. Or point the money at the 529 we also hold, which has its own lanes. Any of these beats what I did, which was click confirm during a preseason game with a plate of wings going cold beside me.

the check written from her money

We paid the tax from the account itself, which the law permits and which I decided was the honest accounting. In March I sold another $1,600 of shares, printed the 1040 voucher, and had Amara sit with me while I mailed the check, envelope in her hand, walk to the mailbox at the corner on a day with wind coming off the lake. She asked whether the government would spend it on anything good. I said presumably not on anything she would notice. She wrote the amount in her own logbook, under a page where she tracks the balance every December, and I watched her do it and figured about the eight years of hot-chocolate statements that never once noted what withdrawal would cost. The lesson landed. On me, mainly.

the dining table, next March

Next year we do this again on purpose, and small. There is $2,600 of planned gain left in the account for a summer program, and we will take it in August 2026 and again in August 2027, each slice under the threshold, each one logged in her book, and then she turns 18 in the spring of 2030 and the trapdoor closes forever. Yesterday she asked whether her account was still worth having, and I said it was worth having and worth understanding, which are different products that brokers sell as one. The table is clear now, the folder is filed, and Form 8615 sits in her logbook behind her balance page, the first government paperwork she has ever owned. On Sunday, Mar 8, at 2:10 in the afternoon, that form was a line I read aloud in a room with one headphone comin off. Now it is a page she can explain to her friends, which is the best $1,240 I never spent.