You can send an invoice to multiple recipients with Hiveage, by typing in the additional email addresses straight into the To or BCC fields on the Send Invoice screen.
Sending to Contacts and Team Members
If you have added multiple contacts for a connection (client or vendor), their email addresses will pop up as you type in the To field.
Similarly, if you have added team members, their email addresses will be pulled into the BCC field as you type.
All of the above features are available for Estimates and Bills too.