Hi! Thanks for your question! As a native English speaker, I would refrain from using either statements (however, out of the two the first would make the most sense to someone). Rather, I would go with the following options: "You have given me too much money/change," if you want to use the 'too much' option. "You have given me $20 instead of...", if you want to state the exact amount. Furthermore, you could use: "You have undercharged me" "You've overpaid me by $20" Sadly, there is no specific term I can think of for the opposite of being 'short changed' (the moment when you are given too LITTLE change". I hope that this helps? Matt

As a rule it is" too much" for something you can't count, like water, flour, rice etc and "too many" for something you can, like apples, shoes, e-mails. Even though you can count money, the nature of an amount of cash means it takes "too much".