If you have credit card tips processing in your point of sale or payment system, you must have this feature turned on to transfer your sales successfully into QuickBooks. Commerce Sync recommends always leaving this feature on (checked), regardless of whether you have tips processing.
You will see the credit card tips as a line on the invoice Commerce Sync transfers. The item that Commerce Sync uses will always be an item that lives in a Liability account in QuickBooks.
Here is the setting in the Commerce Sync Dashboard:
When you are doing your bookkeeping task, depositing your cash or doing payroll, you will offset the increase in the Tips Liability account with a decrease in paying out tips to employees.
The accounts, items, and customers in your Commerce Sync settings are populated by the information Commerce Sync receives from QuickBooks.