Contributions to a 529 plan are not deductible on the federal return.

Per the IRS website 529 Plans: Questions and Answers:

What is the main advantage of a typical 529 plan?

Earnings are not subject to federal tax and generally not subject to state tax when used for the qualified education expenses of the designated beneficiary, such as tuition, fees, books, as well as room and board. Contributions to a 529 plan, however, are not deductible.