I am a sole-proprietor, operating an Amazon online business. Are the State Sales Taxes paid, considered a deductible expense? And if so, where do I include on return?

If you included the sales taxes collected in your total income on the Sch C then in the expenses section you can deduct the sales taxes paid to the states ... watch for that category in the expenses section.

However if you only entered the income you received net of the sales tax you cannot deduct the sales taxes again. 

Thank you.  Your response is very much appreciated.  By any chance do you know where the state sales tax deduction is located within the expenses section?  I haven't found it yet, don't want to miss it, and would rather not include it under Other Deductible Expenses - especially if it has its own section.  Thanks.

You can use the Taxes section or make your own later ... either one is allowed.