When syncing phased invoices with QuickBooks Online, they appear as one invoice per phase there (separate invoices). How can I stop that from happening?
When you send joint and phased invoices from Core to QuickBooks Online, it creates multiple invoices in QuickBooks Online by default, depending on the number of projects or phases on the invoice. You can prevent that by checking the option in Integrations > QuickBooks > QuickBooks Sync Detail > Sync Settings > Send under the Invoice drop-down: Send joint invoices as single invoice to QuickBooks. Check out this article for more details.