This is the part of a stairlift purchase most often handled badly, and it is worth several hundred dollars.
Under federal rules, medical and assistive devices specially designed for a person with a disability or chronic impairment are zero-rated for GST/HST when supplied on the written order of a medical practitioner. In practice that means a note from a doctor, occupational therapist or physiotherapist naming the patient, stating the condition and signed by the professional. Services related to a zero-rated device, including installation, are generally zero-rated too.
Zero-rated is not the same as a rebate. If the documentation is in place at the point of sale, the tax is simply not charged. If you pay it unnecessarily, recovering it afterwards is considerably more work.
Beyond sales tax, two credits are worth knowing about. A stairlift installed for medical reasons can generally be claimed under the Medical Expense Tax Credit. The Home Accessibility Tax Credit allows qualifying individuals, broadly those aged 65 or over or eligible for the Disability Tax Credit, to claim 15 per cent of up to $20,000 of eligible renovation expenses, a maximum credit of $3,000. Provincial credits may apply on top. Tax treatment depends on your circumstances, so confirm the detail with the Canada Revenue Agency or an accountant before you file.