A five-year-old U.K. kid who missed a friend's birthday party at a ski and snowboard slope over Christmas break received a bill for $24 from the birthday boy's family. The invoice was slipped into Alex Nash's backpack at nursery school and brought home to his parents, who couldn't believe it wasn't a joke.

But Alex's dad, Derek Nash, confronted the birthday boy's mom and found out she was serious about charging him a £16 "no-show fee" based on a conversation they'd had before the holidays.

"She saw me and asked if Alex was coming to the party. At this time I agreed and said that Alex was looking forward to it," he told the Plymouth Herald.

But Alex's plans changed, and he ended up spending the day with his grandparents instead. Nash said he didn't have contact info for the birthday boy's parents, so he wasn't able to call and let them know.

"My partner looked out for [the friend's mother] to apologize for Alex not showing up to the party, but didn't see her" at school, Nash said.

And then the bill for a "child's party no-show fee" arrived home with Alex, stuffed in a brown envelope:

After talking to Alex's teacher, who apologized for passing on the bill even though it's against school policy, Nash went to the address on the form to confront the angry mom over, again, roughly $24.

He told her that he was sorry about the cost of Alex not showing up, but he wouldn't be paying the money because of the ridiculous way she decided to ask for it.

After he left, the petty, passive-aggressive fighting over an ultimately trivial amount of money continued on Facebook—the Herald ran the whole conversation, which is embarrassing for everyone involved.

"I don't like fighting with people," wrote the mom who billed someone for no-showing to a child's birthday party. "This is not the first time Alex has not turned up to a party that he has been invited to, either ... the amicable way round this I believe would be to pay me the money and let a lesson be learnt."

"Like I said before, no money was mentioned when we spoke ... I am not a child, so please do not speak to me like I am one," Alex's mom replied.

Now the Nashes claim the other mom is threatening to take them to small claims court, a process that costs more than the paltry amount of money they allegedly owe her. It's the principle of the thing, I guess?

A lesson has been learned in this situation. Unfortunately, it's a stupid lesson, and it's the kids who've learned it from their bickering parents: Alex says his friend will no longer play with him at school.

[h/t Yahoo News]