Invoiced Business Network makes it easy to collaborate on invoices and other documents. The built-in messaging features allows buyers and sellers to communicate about a specific transaction. Once you have sent an invoice the messaging feature is available.
When viewing an invoice, there is a "Messages" card that shows the full conversation and allows either buyer or seller to provide an update or ask a question. After you send a message, the other party of the transaction will receive a notification about your message with the ability to reply.