"Monies" refers to different types (eg. notes and coins considered separately), different sources, or different currencies of money. Which is why you'd find it in specific cases like legal documents, but not in everyday use. When talking about money in general, it's an uncountable noun so "money" stands for both singular and plural. Some money, no money, plenty money, lots of money.

It's "monies" But monies is a word that is only used in legal documents, like leases and loan agreements. In normal conversation, money can be both singular and plural, and you would use this word in everyday conversation. Examples: I have one dollar. That isn't a lot of money. I have five hundred dollars. That's a lot of money! And your sentence would read: I deposited a lot of money today!