Company bosses were told to be on their guard yesterday after figures showed that employee fraud has risen by 81 per cent in the last two years.
The Christmas break and Bank Holiday offers the perfect opportunity for thieves to cover their tracks because fewer staff are in the office, research suggested.
Managers also "take their eye off the ball" in the run-up to the New Year, allowing fraud to slip through the net.
That means bosses should be checking this week on whether anything is amiss.
Andrew Durant, head of the fraud investigation team at accountants BDO Stoy Hayward, which issued the study, said fraud involving #50,000 or more was on the rise.
Patterns of fraud generally fall into four categories, with the first being procurement, where an employee may approach a manager to sign off invoices in a hurry.
The second involves temping staff who may be given passwords to financial accounts.
The third is where fraud-sters work alone to produce paperwork to cover their tracks. The final type is where staff providing cover for managers on holiday are given greater access to sales systems, making up their own discounts.
Mr Durant said: "I know from personal experience that Christmas is a favourite time for fraudsters." ..SUPL: