Invoice Details is where you can set the tax rate, how much a late fee is, and add any default notes to all invoices for your students/prospects. To set up these rates hover over Settings in the right menu and click on Invoice Details.
This will bring you to the Invoice Details page. Determine when the payments are due (the term), the late fee, if you want to include tax in your invoices, the tax rate, and any notes you want to show on the invoices. Then click Update Invoice Details to save any changes you made.