Which form of money is not used in the u. s.?

$50 bills
dollar coins
euros
checking account deposits

Euros. Euros is not in the US because it is the currency for most European countries. 

It is the rest because:

$50 dollar bills: There is a US 50 dollar bill, which has our 18th US president Ulysses S. Grant on there.

Dollar coins: The older the better there was a act passed in the US that enabled valuable material such as gold or silver to be placed on the coins, leading to immense costs.

Checking account deposits: Literally, if we don't have these, we don't have banks, and if we don't have banks, every other day someone is going to be digging a hole in their backyard to bury their savings.

hope this helps