No, you cannot deduct your 403(b) contributions on your tax return. These contributions are already accounted for on your W-2 in box 12. The pre-tax portion has code E and the after-tax portion has code BB (Roth 403(b)). You are already receiving a tax benefit on the pre-tax portion. By design, the Roth 403(b) contribution is not deductible.
Please see the FAQs below for more information.
Where do I enter my 403(b) contributions? https://ttlc.intuit.com/replies/5459114