What fields can I add to my invoices?

When generating an invoice you can specify from the "Invoice" tab of "My Settings" which fields appear on your invoices.

You can decide whether you include:

• Client name & address
• Date of birth 
• Hospital #
• NHS #

Additionally you can select up to 3 custom fields to include which is explained in the article linked below: 

How do I add custom fields to my invoice?