I’m amending my New Jersey state tax returns to request a refund based on the Difficulty of Care income exclusion. Besides my W-2, what other proof can I provide?

I am in the process of amending my prior-year New Jersey state tax returns to request a refund based on the Difficulty of Care income tax exclusion. I mistakenly paid taxes on income that should have been excluded and am now seeking a refund for the past three years. The state has received my amended returns but is requesting additional documentation to support the exclusion. Aside from my W-2, what other forms of proof can I provide? I provide live-in caregiver services through the Division of Developmental Disabilities (DDD) and the Personal Preference Program. Any guidance or assistance would be greatly appreciated.