Check that your takings are what they should be.
Keep track of price changes.
Keep an eye on stockholding.
Check that you are being charged correctly for what you receive.
Tills zeroed at time of stocktake.
Profit margins on every sale item.
Check that your profit margins are correct.
Keep track of individual sales.
Keep an eye on barrelage.
Show the tax and the vat authorities that you are managing your business responsibly.
Provide independent, unbiased reports.