The best way to avoid issues like this is to keep a clear and detailed record. Have a record of the money that comes in and what it is ment for, then have a clear record of the amount of money that goes and what it is ment for. Where i used to work as a photo editor, though i was the manager, my boss then had a strict rule that we must tell him when we need any materials, and he will be the one to contact the supplier. You can also implement this method, this way you can easily monitor how money is spent. While this is an effective method, it also has it’s down side. It can delay work flow, especially if your workers are not able to reach you in case of an emergency.