A third of workers in the UK feel it is acceptable to increase expense claims as a result of pay freezes and the current economic crisis.
Research by GlobalExpense shows a fifth of employees who claim expenses have already exaggerated them by an average of £14 per expense.
A tenth of workers say it is likely or very likely they will increase claims if they get into financial trouble or think they can get away with it.
David Vine, managing director at GlobalExpense, said adding £14 may not sound like much but with 3.7 million employees making claims it soon adds up.
"The amount of money that businesses are losing every day through fraudulent claims will be tens of millions of pounds," he added.
According to the survey, the most common reason people exaggerate their expenses is because the mileage rate paid by the employer does not cover the actual costs.
GlobalExpense is an expense management company responsible for processing the claims of more than 1.5 per cent of the UK workforce.