Invoicing Excess Quantity at Customer

Dear All,

What is the best practice to implement if you encounter a scenario like, "customer claims that your plant have shipped excess quantity. But your GR in the system for that DN/Invoice has exact quantity. How are you going to invoice the excess quantity that the customer is claiming without returning the units for recounting?. Is it proper to just do adjustment on system stock for the product to be able to invoice the excess quantity?"

Please advise.

Thanks and regards,

ching