Businesses were urged to check accounting packages after it emerged that a date-related programming error could cause a widely used accounting package to get its sums wrong.
Software supplier Pegasus said this week it was possible that some users may not have received a software patch to correct an error in Pegasus Senior, an accounts package used by many small and medium-sized businesses.
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The error, which strikes from this month, could cause the programme's "age debt" calculations to overlook debts that are a year or more old.
"Any users who have encountered this problem should contact their resellers immediately to gain access to the latest version of Senior," the supplier said in a statement.
Paul Booth, technical manager for the faculty of information technology at the Institution of Chartered Accountants for England and Wales, said the problem could catch users on the hop.
"People would notice if something didn't work, or something has a ridiculous date. But they might not notice an aged debtor a year ago," he said.
Although the problem is relatively minor, it does raise questions about what other year 2000 problems could be found in accounting software packages, said Booth.
Companies need to keep an eye on their software and should not relax after key trigger dates. "Problems may come to light long after the trigger date," he said.
Pegasus said it became aware of the problem in April last year, and a fix should have been sent free of charge to the 75% of Senior users holding annual licence fees.
However, the company said it was possible that some of the remaining 25% of users had not had their equipment updated.
Pegasus users who contacted Computer Weekly said that they were not aware of the fix.