The Company ID is a required field in the Login Info section in Bill.com.

To locate the Company ID in Sage Intacct:

1. Hover over Company and then click Company Info 
2. The Company ID will be found in the ID field
3. Make sure this ID is entered in the Company ID field in the Sync > Login Info section in Bill.com.

For more information on configuring your Sage Intacct sync, please refer to the the Sync Intacct Sync - User Guide.