How can I make changes to the Invoices settings?

Going to Settings -> Sales -> Invoices

Invoices Prefix

Is the prefix that is at the forefront of Invoices names, through which you can identify the quality of information and distinguish it from expenses and Estimates.

Show if it has been viewed by the client

Through this feature, you can know if the Client has opened the invoice or not.
When you activate this option, you will see an invoice page. A closed or open envelope icon will appear
Next to the grade status, and you will also see text appear on the grade page, see the following images:

Note: This feature is only visible to managers and the team, not visible to clients.

Terms and conditions

It allows you to add the terms, conditions and your contracts to the Invoices
To appear by default when you send any Invoice to Client’s.