What is a schedule IN-OCC Ceritfication year?

For the certification year, you need to enter the tax year for which your credit has been certified.   You'll find this information in the certification letter you received from the entity that authorized the credit, or on Form IN K-1, if applicable. 

To claim the credit you're entering on Schedule IN-OCC, you should have requested and received certification to claim the credit from the appropriate authority. If so, you would have received a certification letter from the authorizing entity (or on your IN K-1, if applicable.) 

See the Instructions for Other Certified Credits on the back of the schedule linked above for more information.