If you ever create invoices in QuickBooks Online, never let QuickBooks Online choose invoice numbers. ConnectWise PSA auto-numbers sequentially, and QuickBooks Online auto-numbers from the last created invoice. If you manually enter invoice 1 in QuickBooks then batch over invoice 1000, QuickBooks will want to number your next manual invoice 1001 but ConnectWise PSA will want to number it's next invoice the same thing. Invoice numbers must not be duplicated between the two systems.
