I am an independent contractor that gets a flat rate daily rate when I provide services, plus my client will pay my travel costs above and beyond the daily rate. Is my daily per diem taxable income.

Its been a long time since I got per diem, but I seem to remember it is taxible income. And that it can be adjusted downward by real, documented and IRS acceptable reciepts for actual expenses. But its been over a decade and rules may have changed.

Collecting per diem is income to you whether you spent anything or not, so yes, it should be taxable. Of course, as smoothy points out, your IRS approved "reasonable" expenses reduce your net taxable income, assuming you can itemize and document them.