NEW YORK - Millions of H&R Block Inc. customers who in past years relied on short-term loans backed by their expected tax refunds will not have that option when they file their 2010 returns.

The reason: Block's banking partner was forced by federal regulators to stop offering the loans.

It's a blow to Block, the nation's largest tax-preparation company, which could lose tax customers to competitors still offering the loans and has virtually no time to find a new funding partner before tax season starts in January.

That means Block could lose millions of dollars in revenue, since nearly 45 percent of its customers use a refund anticipation loan or refund anticipation checks. The company made about $146 million on the two products in 2010.

RALs, often referred to as "rapid refunds," are short-term loans backed by an expected federal income-tax refund. A refund anticipation "check" is actually an account where a refund is deposited. This enables taxpayers to have their tax return preparation fees deducted from their refund, rather than paying up front. Both products are typically used by low-income customers who file their taxes early in the season.

Block's contract with HSBC Bank to back its RALs dates to 2005, but bank regulators ordered HSBC to stop funding the high-interest loans, which typically are offered to customers with spotty or no credit histories.

A spokesman for the federal Office of Comptroller of the Currency, the Treasury Department agency that regulates national banks, would not provide any explanation for the directive, stating that such actions by the agency are confidential.

A change in policy last summer by the IRS probably contributed to the OCC's decision. The IRS eliminated a code that let tax preparers know if customers would get their entire refund, or if some money would be withheld to cover things such as unpaid back taxes. Tax-preparation companies used the code as a form of credit check for the loans.