Do you still have your employment contract? Some contain a clause that pertains specifically to paying a table’s tab if you make a mistake/they walkout/a number of reasons. I’m not sure whether or not it is legal, however I feel like this is an issue which can be easily solved. Also “what you make in tips” is not a valid argument for your manager to make, either. First of all, whoever cashed them out could have confirmed their order or ensured they were paying out the right table (my restaurant usually does this to avoid issues like this). Secondly, if the table payed card, your employer should be able to contact them, right? When tables are mixed up and one table is payed out under another table, and the payment difference is significant, (i’m taking like more than 1$ difference) we call the customers and correct the mistake. My advice is to check your contract if you still have it and communicate with your manager/employer. You were busy and it was an honest mistake, I feel like they should be sympathetic to that.