My 9-Year-Old Charged Me 10 Percent Interest from Her Save Jar

Sixty cents, in pencil, on the back of a farm-stand receipt, taped to a mason jar with SAVE written on it in green marker. I found it at 5:40 p.m. on an August Tuesday in 2025, standing at the kitchen counter putting down groceries, and the note had my name at the top spelled correctly, which somehow made it worse. IOU, it said. $6.00 plus 0.60 = $6.60. Ten percent. That is the bank rate.

Some context, because the six dollars needs a frame. My daughter Junie was nine that summer, and in January 2025 we began the three-jar system every parenting article had been yelling at me about: SPEND, SAVE, GIVE, three mason jars on the shelf above her desk, fed by an allowance of $3 a week, $1 to each jar, paid every Sunday whether she cleared her plate or not. The jars are not a metaphor in this house. They are the actual bank.

The part I did not see coming was on the back of that receipt, and I only understood it later: she had absorbed the interest rate from a worksheet still folded in her backpack, and she applied it to the one customer who had ever overdrafted her, which was me.

three jars, green marker, january 2025

We set it up on a Sunday at the kitchen table with a Sharpie and three jars from the pasta sauce shelf. The rules fit on an index card: SPEND is yours, no permission. SAVE does not get touched until the bike. GIVE stays until she picks the place. Seventy-eight weeks later, the card is soft at the corners and still on the shelf, and the system has survived one lost jar lid, a cat named Biscuit, and exactly one defaulting borrower.

the farm stand was six dollars short

Here is how the debt happened. August 9, 2025, the farm stand on Route 12, peaches and sweet corn, $21.40 total, and their card reader was down, and I had $15.40 in cash in the truck cup holder. Junie was with me, and she had her SAVE jar money in her pocket because we were going to count it when we got home. Six dollars. She counted it outta her own hand into mine, and she did not say one word about the bike fund, and I said we would square up in two weeks like it was nothing.

problem 4 on the worksheet

The worksheet was from math family night at Grandview Elementary, still folded in the front pocket of her backpack when I went looking for the source of the 10 percent. Compound interest, problem 4: if you save $1.00 at 10 percent interest, how much after one year? She had gotten it right, $1.10, in pencil, and below it, in the margin, she had written and be fair about it. I asked her where the rate came from and she said it is what the bank gives Grandma, on her statements, in the green box. Sixty cents on six dollars for two weeks was her own arithmetic, not the worksheet's. I asked about that part and she shrugged and said the bank would do it.

the ledger with the staple

She got paid on the next Sunday, and the transaction went into a spiral notebook she labeled LEDGER in the same green marker. Date, who, how much, paid back, interest, total. My line is stapled in, the actual farm-stand receipt, cuz I paid the $6.60 in full on August 24 in quarters and ones and she signed the line like a teller. Biscuit the cat has knocked the ledger off the shelf twice. The staple held.

seventy-eight weeks of three dollars

Eighteen months of the system, counted this June: $234 of allowance in, $3 a week, $1 a jar. The SPEND jar saw $78 come and go: two Squishmallows at $14 each, a vending machine phase I estimate at $19, assorted gas-station candy. The SAVE jar holds $78.60, which includes my sixty cents, untouched, still short of the $140 bike on the tag at the shop on Fifth. The GIVE jar did its job too. Interest she charged me: one payment, ever, and the client was her own mother.

the humane society got twenty dollars

In June she carried $20 from the GIVE jar to the humane society on Cooper Road, in an envelope, with a note listing her three cats by name including Biscuit, who is fine and terrible. The receipt is taped inside the GIVE jar now, which holds $58 and its next deposit. She picked the humane society over the school fundraiser without hesitation, and when I asked why, she said the fundraiser never showed her the animals. Hard to argue with the audit standard.

she asked why my jars have no labels

The question came at dinner in July, offhand, the way the real ones arrive. She wanted to know what my jars were labeled, and I began saying retirement, and she waited, and I grasped I could not answer in the system's own language: which jar, what rate, paid on what day. That night I moved my transfers around: $300 on the first to the online savings, now labeled in my banking app, 4.0 percent, and $150 more than before into the account I stopped looking at in 2023. My 9-year-old runs a stricter credit desk than I did. She has never once missed a Sunday payout, and I am the only delinquent account on her books. The jars are chipped and the green marker has faded to gray. There is a new note on the fridge, dated July 26, stapled to a gas station receipt. I checked it twice. The math is right.