Setup invoice required fields allow you delegate invoice creation to sales people

In case you want to delegate process of creating invoices down to sales people, there is an option. 

Usually, during sales process, sales people need to focus on sales, not administration. 

But, once the deal is closed an you want to collect cash, it is good idea to send proper invoice. That means, the invoice should have all required fields filled-in. 

Now you can set-up fields that are going to be required when creating new invoice.

You can search for "Form" in Options & tools and find Form Settings screen, where you can configure what fields are required.