We are awaiting retroactive DTC payments for our son. For 2020, 2022, and 2023, my husband’s income was higher. Should we claim credits under him to maximize refund?

The T2201 Disability Tax Credit Certificate form that was filled for your son will have a supporting family member listed, and that's who should claim the transfer. If you want to transfer the DTC to someone else, you would need to submit a written request to the CRA for the transfer. This request must be signed and include details of the support they provide for the basic necessities of life.