Staff tab/credit system help

I run a small convenience shop in the UK and have 10 employees. We allow them to have a tab, if they’d like a drink or food while on shift, they can have it on credit until they get their weekly wages. Currently, They scan the item, void it, add their name to the void receipt and put in on a hook behind the counter. When they pay, they add the paid receipt to the tab receipt and put back on the hook so I can check it. It’s all turned into a mess. One employee doesn’t pay for ages, another keeps adding, but things like household items to take home, even letting her son add to the tab on their way to school. I’ve spoke to them and repeated how the tab system should be used by it hasn’t improved. The void receipts go “missing” or they say they’ve paid but forgot to add the paid receipt. Meaning I have to spend a lot of time on the cctv to check. Is there an easier and fool proof system I can use? Other than taking away the benefit of having one