The amount of money to be put in a petty cash fund depends on the needs and expenses of your business. It should be an amount that is sufficient to cover small day-to-day expenses.  However, this amount can be more or less depending on the size of the company and the nature of its expenses. The amount should not be so large that it poses a security risk to a company’s finances but should be enough to cover trivial expenses. Most companies will set aside around $50-$500.