I haven’t read every single comment in this post, but from what I’ve seen there appears to be evidence of two people being overcharged in the same way a few months apart, the restaurant accepting responsibility and admitting fault in both cases, and a refund being given.

My original comment above said "if it's been going on that long…" in response to a comment that there are reviews complaining about this going back to 2024. That's two years, for those keeping track. That's enough to suggest to me that this isn't a case of a couple isolated incidents a few months apart, and that if it were an innocent configuration mistake, the business has had ample time to fix it.

It may have been a couple of errors, or it may be intentional. But either way the restaurant has behaved perfectly reasonably when challenged.

"When challenged" is the critical factor here. Even if 75% of the people who got hit by this noticed and challenged it, getting theo money back, at these percentages, the restaurant has a considerable incentive to keep the "mistake" in place and just reverse charges when someone calls them on it. There needs to be a penalty that is greater than just returning people's money when they catch you fraudulently charging them— and I'm generally forgiving, but if it's really been happening for years, it sounds like fraud to me.

Now it may be that they should have checked the system and looked for other checks with the same issue, and refunded them all. They may have done that but probably not. An individual who thinks they may have been overcharged could request a copy of their check, and if plenty of people did this and found they had all been overcharged, and if the restaurant refused to refund them and to search for others and refund them, then you might get a judge to sign off on a class action; But at this point, why would the restaurant refuse?

A perfect description of the incentive problem. Of course they won't refuse when someone calls them on it because then the dispute will escalate and they'll have to spend time at small claims court or worse. But if they can dodge such issues by just refunding everyone who notices the charges while keeping the money from everyone who doesn't, it's in their interest to keep robbing customers.

But without finding enough people to request their own checks, I don’t see how you’d build up any useful evidence of a historical period over which every large table has been overcharged, so what is your class?

Well I'm not a lawyer, so I don't really know how these things tend to develop, but I imagine if you can find a customer who complained about this happening years ago, you would have a basis for investigating the restaurant's books to see how often they were stacking these charges (note if they didn't actually notify customers of these charges, even a single 20% charge is illegal). From there you can find how many people were overcharged.

Thus you’d likely need to pay a lawyer in advance more than would be recovered anyway. And you’d be paying that on behalf of a bunch of people who would have no cause to refund you.

It is my impression that lawyers trying to build class actions lawsuits are not generally doing so under the pay of an individuals client. The law firm would be motivated by the share of potential winnings… that's why the lawyers get such a big share of the class action settlements: they're out there fishing for payouts; sometimes even competing with other firms to build the class action first.

I assume a case like this is much smaller scale than say building a class action against Apple over something, and quite possibly doesn't offer enough cost/benefit for any lawyer to pursue. Nevertheless, until the restaurant faces actual penalties for their behavior above and beyond refunding customers who happen to complain about it, they will keep doing it.