When enabled, a new option will be available in the System Options Tab Additional Features menu called Gross Profit Configuration.

Enable this option to allow you to configure how Gross Profit is calculated on the invoice, similar to how it is configured in reports. See the Gross Profit Configuration topic in this chapter for details.

When this option is disabled, it will default to the Classic Gross Profit calculations, which is InvTotal - Landed or Base Cost (depending on  the state of System Option #171), and also include Billbacks (depending on the state of System Option #180).