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I recently got a raise, which is great. However, I got my paycheck today and it seems to indicate that my raise is double what they told me it would be. My first instinct is that they are trying to make the raise retroactively apply to the previous pay period, but in case the next paycheck has a similar overpayment, what should I do?
I've asked others and they told me I shouldn't say anything about it, because the only possible change is that I get less money. But my concern is that they will discover an error and demand repayment. Can they force me to repay it all at once? Do they garnish wages over time instead? Should I be putting this excess money away if I don't bring it up?
Basically, what is the worst thing that can happen if it turns out I am being overpaid by accident?
EDIT: someone suggested this was a duplicate of another question, but that other question is specifically asking about the tax ramifications of overpayment bumping someone up to another tax bracket. This question has nothing to do with taxes.