Even though I am going to ask about it on Monday, my thoughts are more like "why should I have to ask about this? Why can't I just let it go and let them deal with it? It's not my job." And I don't really understand if I'd be in the wrong for not reporting it. (Even though I am going to report it on Monday.)
Ugh, and I'm remembering another time around Christmas, where I received a bonus for high performance. I told them in my review that their numbers were off and my performance was probably not as high as they said it was. They were like "well its an average of the whole time period" and I just said something like "oh okay." Idk, they didn't count right and I got ~$700 before taxes. I didn't feel like I needed to correct them because a) that's their fault if they can't count and b) I kind of brought it up already to them in my review. Not sure what to do about that one, either.
I didn't do anything, and now I have one or two moral issues in my hands. They're not even my fault.
That to me sounds more like your just exasperated with an ongoing problem you see, that your employers seem unwilling to correct.
But while it isn't your job to oversee accounting at work, your doing the right thing.
My biggest ongoing moral dilemma where overpayment was concerned wasn't as big as all that, just the occasional cashier giving back too much change at the gas station (back when cash was a thing... Lol).
The minimum wage employees at the gas station often couldn't manage to count, and more than once in life I was given an extra 10 dollars or so in change.
I understand that the accounting department at your place of employment can't count either, lol, but when it's in your lap mentioning it is the right thing.
Your biggest issue causing you to feel exasperated is that it's an issue they should want to correct and aren't.
This doesn't sound like you're anything but exasperated with a recurring problem though, and that's something I believe anyone would feel.
But, like most things in life, it's your response that matters as a Christian. If you mention it and they don't believe it's a problem, you can put it behind you.
They may really have appreciated your help so much they don't want to take the bonus money away, or it's possible for you to have been the one who misunderstood something and the money is actually owed you.
Money that is actually owed you is possible, a few years ago I thought I had been overpaid only to find out I was wrong and it was owed me.
So really you just never know until you bring it up, and, while it isn't your job to oversee, it is your responsibility to bring up since you believe an error was in fact made.