How to Collect a Tip After Payroll has been generated

Invoicing - 
Record the tip in QBO.  (All Invoices are created in QBO)

Process the tip directly in your Credit Card Processor

Add the additional pay items in MC to the technician(s) who worked the job.

If a tip is left after payroll is closed, you will need to record the tip in QBO. (All Invoices are created in QBO) and process the amount of the tip directly in your credit card processor in order to collect those additional funds from the customer, 

Finally, to ensure your technicians are paid for those tips earned, you'll add the additional pay items in MC to the technician(s) who worked the job.  Company > Invoicing & Payroll > All Reports > Additional Pay.