Can I claim fees paid for ABA therapy as medical expense?

As per this Canada Revenue Agency (CRA) webpage - Medical Expenses 2021, you can claim therapy if it meets these conditions:

Therapy – the salary and wages paid for the therapy given to a person who is eligible for the disability tax credit (DTC). The person giving the therapy must not be your spouse or common-law partner and must be 18 years of age or older when the amounts are paid.

The therapy has to be prescribed and supervised by one of the following practitioners:

• a psychologist, a medical doctor, or a nurse practitioner (for expenses incurred after September 7, 2017) for a mental impairment
• an occupational therapist, a medical doctor, or a nurse practitioner (for expenses incurred after September 7, 2017) for a physical impairment

If you are still unsure if you can claim this expense, you can contact the Canada Revenue Agency (CRA) and confirm it with them. If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency