Tax disappears from invoice

I recently got ERPNext installed and working correctly on my server. Really like the ERP but have run into a problem that i can’t find a solution for. After creating a project, some tasks and a time-sheet, I click the “create sales invoice” at the top of the timesheet. The sales invoice is created successfully with the tax added to the invoice on the hours and billing rate i entered in the timesheet.
But when i click save invoice the tax disappears from the saved invoice and i only have the tax free amount on the invoice. Is there something i haven’t set up correctly? most things are the default settings so far as i just got started.