H&R Block Inc., the world's largest tax preparer, has shut down its online filing system after discovering that some people's financial information may have been mixed with that of other people. H&R Block identified fewer than 50 people affected among more than 300,000 tax returns, but it expects the program to remain shut down until the weekend while it makes sure no other people are affected, spokeswoman Linda McDougal said. The company is continuing to audit returns and will not restore the program until it is sure that returns are accurate, it said. Tax offices of H&R Block and its software program, TaxCut, are not affected, the company said. H&R Block is offering free downloads of the TaxCut program. "We've got what we think is a very rare circumstance and confined to our internal system," McDougal said. Kansas City, Mo.-based H&R Block said Feb. 3 that it expected to process about 650,000 returns over the Internet site this tax season. The IRS estimates that more people than ever will file their returns online.