FDIC: $20 purchase, $27 fee = 3,520% APR

Sure, your bank lets you overdraw your checking account, but at what cost?

To the tune of $40 billion a year, practically pilfered from consumers' pockets, according to a report by USA Today.

The banking industry is making that fat cash on "courtesy overdrafts" which automatically cover your transaction when you spend more money than you have in your account.

But then you get socked with a steep fee for the "courtesy" -- an average $34 a pop, according to the Center For Responsible Lending (CRL).

It's like getting a loan without asking for it.

Instead of denying a transaction or sending you a warning when you don't have enough money to cover it, many banks also accept the transaction using a system that debits a day's transactions from the highest dollar amount to the lowest, artificially increasing the number debit fees collected, according CRL.

USA Today says some even charge consumers the overdraft fee before they overdraw.

What?

They deduct a purchase when it's made, rather than when it clears. That will push your account into the red even sooner.

The practice is growing during the Great Recession, even as regulators try to put a knee to the neck of banks, thanks to a gang of bank-paid consultants who school banks on how to separate you from your money.

Remember how lenders gave away those funny-money mortgages and where that practice led the economy?

Overdraft fees are the single-largest driver of consumer-fee income for banks, a whopping $38.5 billion is projected for this year -- nearly twice the $20.5 billion they snatch as credit card penalties, including late and over-limit fees, according to USA Today.

Payday lending is a $28 billion-a-year business, according to CRL.

The Federal Deposit Insurance Corp. says if banks cover a $20 purchase and charge a $27 fee, the loan has a 3,520% annual percentage rate (APR) if paid back in two weeks.

CRL says the average overdraft fee is $34 when the average transaction is only $20.

Overdraft fees are most commonly triggered by debit card transactions and ATM withdrawals.

It's like a payday loan.

From a bank.

Gotcha!

• Help stop Gotcha Bank Fees.

• Learn more about overdraft fees.

• Take a closer look at the world of payday lending and overdraft fees.

• Ask your bank to stop approving transactions that throw you over your limit. If they refuse, change banks.

• Consider signing up for true overdraft protection that links your checking account to another account -- savings, line of credit, even a credit card that gets the bill when you over draw. You may still pay a fee, but a much smaller one.

• Use online accounts to keep daily tabs on spending accounts you use daily. Balance your check book regularly. Enter transactions the day you make them.

• Stop living paycheck to paycheck. You'll never get ahead with those overdraft fees on your back.

• Take a month off of spending and buy only truly needed items -- don't eat out, forget Starbucks and entertain yourself at home.