@AndySFMC there is not an exact report for something like this. However, under sales summary there is the "service mode summary". This shows the difference between table service and quick order. Starting a tab just leaves the check open with a CC saved in case of a walk-out. It may come down to a demographic analysis? Does your clientele want to see one bill that is higher or do they care if they open their card 3-4 times a night?
Personally, my bars use running tabs for every single guest who comes in. Our average gratuity is 22.6%.
