'Invoice Notes' are useful for segmenting which clients / companies are associated with each office, in a shared Fathom organisation.
To add an invoice note, follow these steps:
From the Home screen, click the Company Settings icon (or 'Company Settings' tile if you have just one company).
Go to 'Step 2: Company Profile'
Click 'Edit' next to the Invoice Note field
Add a note (eg. Brisbane, Melbourne, Sydney) & save changes