The federal government offers a tax credit to people with disabilities. If your first application is approved, they send out a request for DTC Part 2, which includes a review of records, a multi-page questionnaire and a copy of your chart, sent by regular mail.  Typical Fees across providers: 
Part 1 - Review records and Complex mental health or psychiatric disability application$200–$500+
Part 2 - Specialist report supporting DTC application$300–$1,000+