Dear Khun Lhee,
This is causing huge concern to me,
The procedure when cashier receive over/shortage money from customer has been written down in your cashier manual since day one we operated first store in Thailand either it is in cash or credit card payment.
Please make sure that our cashier know the procedure when this kind of transaction incur, what kind of form they need to fill etc.
At the end of the days, shortage must be top up by responsible cashier and excess need to be deposit into company account not otherwise.
Relevant form need to be filled with proper signed from the authorized person in store before send to FA department for further proceeds.
I recommend you do retraining every now and then, to ensure that this practice is well noted and in place.
Thanks