If you wish to rename the "Terms & Conditions" label that appears on your invoices, proceed this way:

In your Dashboard, go to Preferences, in the Documents section, select Invoices and select the "Labels & Columns" tab.

You can change the Terms & Conditions label for Quotes, Delivery Notes, Credit Notes and Purhcase orders by picking each category in Documents, and click on the Labels & Columns tab where you can make the necessary adjustments.