Zoho Books - Branches - Can I cross-charge between branches?

Zoho Books - Branches - Can I cross-charge between branches?

Hi, 
We have two parts of our company, manufacturing and sales.
The manufacturing side will invoice/bill the sales side for the materials and labour on each order. 

I have recently discovered the Branches feature in Books and it fits well with our set up...except I don't seem to be able to create any invoices or bills which can represent a charge from one Branch to another. Any ideas how I could achieve this?

The only way I can see of doing it so far is by creating each Branch as a Customer too...but that seems a bit messy.
Emma