Grandma stuffing money under the mattress isn’t the only one living outside the banking system.

As many as 28 million people in the United States are forgoing traditional financial institutions because of mistrust, cultural and language barriers or a belief that by the time all the bills are paid there will be nothing left for an account.

That can be expensive and risky. People can run up big fees to cash checks, pay bills and meet their other financial needs. Walking around with large amounts of cash can make them a target for thieves.

The bankless are estimated to earn hundreds of billions of dollars a year in income. Seeing a business opportunity, banks are trying to draw in these potential customers. So, too, are check-cashing businesses and retailers, including Wal-Mart.

Many people, however, still resist, preferring to remain in the financial shadows.

They tend to be minority – Hispanic or blacks especially – as well as low income and young.

According to the Federal Reserve, about one in 12 families – 8.7 percent – does not have a bank account.

The number is higher for the poorest – nearly a quarter of families earning less than $18,900, the Fed said, citing 2004 data. (AP)