A supermarket calls you up and says, “We accidentally gave you ¥10,000 too much in change” — do you have to pay back even the part you’ve already spent? That question, drawn from a personal account, sparked a flood of responses on 5ch. Some picked apart the math, saying they couldn’t even imagine a scenario that produces a ¥10,000 overpayment in change, while others focused on the mechanics: how exactly did the store track down the customer’s phone number? Several posters also shared their own experiences with smaller change mix-ups, suggesting people’s reactions shift depending on how much money is actually at stake.
If a store called you after you’d finished shopping to say they’d given you too much change, you’d probably be startled. And if you hadn’t noticed the mistake when you received it and had already spent part of the money, you might wonder whether you really have to pay back money you no longer even have.
The short answer: extra change you receive by mistake doesn’t simply become yours, and in principle you can be asked to return it. That said, factors like when you noticed the error and how the store verified the amount also matter.
Isn't giving ¥10,000 too much in change just… not a realistic scenario?
7AnonymousOct 22, 2026 13:00
Where's your proof? When you hand over the wrong change, what Showa year, month, day, hour, minute, and second did it happen, and how many times has the Earth spun since then? 😤
9AnonymousOct 22, 2026 13:00
Re: #7
Are there seriously people who talk like that?
10AnonymousOct 22, 2026 13:03
Once at a convenience store I bought a ¥500 magazine with a ¥5,000 bill and got ¥9,500 back in change. Just kept it, no issues at all. That was almost 20 years ago now though.
12AnonymousOct 22, 2026 13:04
Clerk: "That'll be ¥996."
Me: *slides it over* ¥1,001.
Clerk: "Huh? You don't need to give the extra ¥1."
Me: "Just ring it up."
Clerk: "……??" *beep beep*
Clerk: "………!!!!"
Clerk: "Your change comes to ¥10,005."
13AnonymousOct 22, 2026 13:05
Once you're at my level, you just tell them honestly right on the spot.
14AnonymousOct 22, 2026 13:05
Better pay it back quick… I checked out at a self-checkout, but I'll return it— wait, huh?
15AnonymousOct 22, 2026 13:08
I've also had a ¥5,000 bill mistaken for a ¥10,000 bill once. I spoke up right away.
16AnonymousOct 22, 2026 13:09
These "Financial Field" articles always read like made-up stories, so it's dumb even bothering to read them. The headline's dumb too.
17AnonymousOct 22, 2026 13:10
Was there ever even a ¥20,000 bill?
64AnonymousOct 22, 2026 14:28
Re: #17
Wasn't that made back in the Obuchi era? Never actually seen one myself, so I can't say for sure.
22AnonymousOct 22, 2026 13:16
I should've pinched my nose and said, "The number you have dialed is not currently in service."
23AnonymousOct 22, 2026 13:27
Do you seriously give supermarkets your phone number every single time? lol
25AnonymousOct 22, 2026 13:28
You can tell it's a Financial Field article just from the thread title alone.
26AnonymousOct 22, 2026 13:30
What kind of situation even leads to ¥10,000 too much in change? Mistook it for a ¥1,000 bill? Wouldn't that only be ¥9,000 too much?
27AnonymousOct 22, 2026 13:32
No need to take this seriously — it's just a made-up story.
28AnonymousOct 22, 2026 13:32
"Got ¥10,000 extra from my favorite checkout girl at the supermarket" — redo the thread title as that, idiot.
29AnonymousOct 22, 2026 13:34
I handed over a ¥5,000 bill, but the clerk must've thought it was a ¥10,000 bill — I got a ¥5,000 bill back as change. Once I got home something felt off, and I finally pieced it together. I called the store, but I'd already thrown away the receipt, so they couldn't verify the details and just told me not to worry about it.
30AnonymousOct 22, 2026 13:37
I've had that exact thing happen once too — came out ¥5,000 ahead.
31AnonymousOct 22, 2026 13:38
Why would a supermarket even be able to identify the customer, let alone know their phone number?
33AnonymousOct 22, 2026 13:40
Years ago I bought two packs of cigarettes and only got charged for one pack's worth. That's about as modest as these stories get for me.
34AnonymousOct 22, 2026 13:42
I want to know the actual mechanism for identifying that customer. Isn't that impossible unless you're a registered member with purchase history? Even if they could just barely identify a person from security camera footage, you normally wouldn't get their contact info from that.
38AnonymousOct 22, 2026 13:52
Re: #34
If you registered your personal info when signing up for the supermarket's point card, and showed that card at checkout, they could identify you that way, couldn't they?
35AnonymousOct 22, 2026 13:44
When you make a point card, you might write down your address, name, age, and phone number (you may well have filled all that in).
37AnonymousOct 22, 2026 13:50
Re: #35
Even so, the clerk would still need to recognize your face to actually identify you, wouldn't they?
36AnonymousOct 22, 2026 13:47
Years ago I tagged along when my older brother bought a desk lamp at a Marui home-goods store. They were out of stock that day, so it got arranged to be shipped to his place once it came in. When the box finally arrived and he opened it, there were two lamps inside even though he'd only paid for one — and that's when I realized that female clerk had basically been hitting on him in a roundabout way, lol.
39AnonymousOct 22, 2026 13:54
If a bank contacted you guys about a "funds recall" (kumi-modoshi — a bank's request to reverse a mistaken transfer), would you actually comply?
40AnonymousOct 22, 2026 13:55
Re: #38
They wouldn't know unless the customer's face could be matched to a name, right?
46AnonymousOct 22, 2026 14:06
Re: #40
If the receipt data records the purchase time, what was bought, and the membership number, cross-referencing that with security camera footage should be more than enough to identify someone, right?
49AnonymousOct 22, 2026 14:08
Re: #46
If the clerk just mixed up the bills, there'd be no record anywhere of who got the extra ¥10,000, right?
51AnonymousOct 22, 2026 14:09
Re: #46
A clerk's change mistake doesn't leave any record at all.
41AnonymousOct 22, 2026 13:57
A store only notices it's ¥10,000 short when they tally up the day's sales after closing, so figuring out which customer got the extra ¥10,000 would be tough.
42AnonymousOct 22, 2026 13:59
What kind of situation even produces ¥10,000 worth of change?
43AnonymousOct 22, 2026 14:00
They probably paid with something like a commemorative ¥100,000 gold coin.
45AnonymousOct 22, 2026 14:04
¥10,000 docked straight from the cashier's paycheck for the screw-up.
47AnonymousOct 22, 2026 14:06
If you tried handing a clerk a commemorative coin as payment, they'd probably refuse it — they'd likely assume it was a fake.
48AnonymousOct 22, 2026 14:07
If the clerk just mixed up the bills, identifying the customer should be impossible — there's no way that clerk would remember who got the extra money.
56AnonymousOct 22, 2026 14:11
Thinking about it normally, this just sounds like a straight-up phone scam to me.
(Haven't actually read the article though.)
57AnonymousOct 22, 2026 14:13
Re: #56
Clerks messing up change is an everyday occurrence — though being off by ¥10,000 is obviously a stretch.
Background and Key Points of the Debate
The original article (Yahoo! News / Financial Field) was essentially a legal explainer arguing that even if you’ve already spent change you received by mistake, you’re still obligated in principle to pay it back. What split the thread was the credibility of the story itself: many pointed out that the math behind a “¥10,000 overpayment in change” doesn’t add up to any plausible real-world payment, while others focused on the technical question of how the store could have identified the customer’s name and phone number in the first place. Combining the personal information registered for a point card with purchase history does make it technically possible for a store to identify a customer, but cases where a cashier’s change mistake gets logged down to “who exactly received it” are, in practice, limited — and the thread never quite nailed down how that gap would be bridged. There was also recurring skepticism about the outlet’s track record of running stories that read as more fiction than fact, leaving it up to readers to decide whether to take this one at face value.
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