Bill.com's integration with QuickBooks for Mac involves a .CSV import/export process. Other QuickBooks options can be considered for Mac users.
Solution A - Import/Export
Objects (e.g., vendors, chart of accounts, customers, items, etc.) are exported from QuickBooks for Mac into .CSV files, edited in Excel, and imported into Bill.com. Bills and payments can then be exported into .CSV files, edited in Excel, and imported into QuickBooks for Mac.
Solution B - Virtual Environment/QuickBooks Online
Use QuickBooks for Windows in a Windows virtual environment (e.g., VMWare) on your Mac. Use QuickBooks Online. Intuit can convert your QuickBooks for Mac file into a QuickBooks for Windows file or QuickBooks Online file.