The solution is a well organised, tightly run petty cash system, where everybody knows the system and how it works. Here are a few quick pointers on what makes a good petty cash system:

• Keep the level of money as low as possible
  The sum should have been decided by those in authority on a rational basis, based on things like level of usage. No matter how small the amount, it should always be insured in case the worst happens.
• Separate funds
  Your system should be run strictly on a 'petty' basis, being used only for small emergency expenses 'as and when'. Major things such as wages and even regular expenses like travel must be kept separate and documented in an expenses sheet

• Imprest system
  The ideal petty cash system is run on the Imprest System principles, based round a float of a certain amount, say £100. This system, involving petty cash vouchers being made out for each cash amount given out, and that being replaced by a receipt for the item when it is bought. This gives the clearest and tightest control, since cash + vouchers + receipts will at any time add up to that £100 value
• Strict security
  Responsibility for petty cas should be carefully allocated. It should be one person, who keeps the box locked away in a generally undisclosed location, and holds the keys. He or she should rigorously enforce the agreed system - of vouchers and receipts - and keep a record of each transaction with a petty cash spreadsheet