You can only deduct $4000 in 529 plan contributions ($2000 before 2018) each year. But you can carry the unused amounts forward to the next year. For example, if you contributed $5000 to your Ohio 529 plan, in 2017, you were only allowed to deduct $2000. You have $3000 "Prior Year Unused Amount" that you can deduct 0n your 2018 return.
