A new study shows banks are cashing in on overdraft fees.  The report released by bank research firm Moebs shows banks have slapped customers with more than $31 billion in over draft fees so far this year. 

That's up from 2011 when customers paid $29.5 billion dollars in overdraft charges.  According to Moebs, there are 144 million customer checking accounts.  Of those accounts, about 25% are frequent overdraft users.

Moebs says the reason overdraft fees are on the rise is checks clear accounts faster.  People think they have time to add funds to their accounts, but instead a check they just wrote is clearing before customers realize. 

A second reason comes in the form of debit cards.  Debit transactions clear accounts much faster than checks do.  In 2011, they made up for 43% of all transactions.  They are also hard to keep track of.

Experts say to prevent from paying over draft fees, be more informed of your account.  You can set up text message and email alerts to notify you when your account is low. The average overdraft fee sit at about $30.