Mental Illness and the Disability Tax Credit Canada 2026

The Mental Functions Category

CRA evaluates mental illness claims under the mental functions necessary for everyday life category. This category covers:

• Memory (remembering everyday tasks, names, appointments)
• Problem-solving, goal-setting, and judgment (planning, organization, sequencing tasks)
• Adaptive functioning (managing finances, personal safety, hygiene, basic daily tasks)
• Social and interpersonal functioning (inability to maintain appropriate interactions)

To qualify, the mental illness must cause a marked restriction in these functions, meaning the person either cannot perform them or takes three times as long as a typical person, and this restriction must exist 90% of the time.

Psychiatric Conditions That Commonly Qualify

• Schizophrenia and schizoaffective disorder (positive and negative symptoms)
• Severe treatment-resistant depression
• Bipolar I disorder with frequent cycling or persistent impairment between episodes
• Severe PTSD with significant functional impairment
• OCD with severe compulsions that consume the majority of daily functioning
• Severe personality disorders (borderline, antisocial) with documented functional restriction
• Severe anxiety disorders where symptoms prevent independent daily living

The 90% Rule for Episodic Conditions

Many psychiatric conditions are episodic, meaning they fluctuate. CRA's rule is that the restriction must exist 90% of the time or more. For episodic mental illness, this means:

• The cumulative impact of episodes must add up to at least 90% of the year
• Inter-episode periods must still show significant residual impairment
• Medication side effects that themselves cause restriction during stable periods can count

This is where documentation becomes critical. A physician must describe not just acute episodes but also the day-to-day baseline level of impairment.

The Role of Medication in DTC Assessment

CRA assesses mental functioning "with appropriate therapy." For mental illness, this typically means with medication and treatment. However:

• If medication is only partially effective and significant impairment remains, the claim can still qualify
• If medication side effects (cognitive dulling, sedation, tremors) themselves cause restriction, this can be documented
• Treatment-resistant conditions where multiple medications have failed carry strong documentation weight

Key Documentation for Mental Illness DTC

• Detailed psychiatrist letter describing functional impairment in daily activities (not just diagnosis)
• Psychologist assessment if cognitive testing has been done
• Records of hospitalizations, crisis interventions, or emergency visits
• Documentation of failed medications or treatment attempts (showing treatment-resistance)
• Records of inability to maintain employment or education due to symptoms
• Disability insurance approvals or workers' compensation records
• Occupational therapy assessment of functional capacity

2026 DTC Amounts

If approved: federal credit $1,481 per year. Combined federal and provincial: $2,080 to $3,741 per year. Retroactive claims for severe mental illness reaching back 10 years can total $14,000 to $37,000 or more.

Real mental illness Filing Scenario

The following example is illustrative. It describes a typical filing flow and does not predict any individual outcome.

A Vancouver resident with a long-standing diagnosis of borderline personality disorder and major depressive disorder met with her psychiatrist to complete Part B. The psychiatrist documented mental-functions restrictions across emotional regulation, decision-making, and routine self-care, supported by a treatment history and a description of functioning during inter-crisis periods. Part B addressed the 90-percent threshold by quantifying ongoing impairment during medication-stable periods, not just during crisis episodes. The Notice of Determination arrived 13 weeks after submission, approving the DTC retroactive to 2021.

Documentation That Works for mental illness Part B

What worked in this Part B: documenting functional impairment during inter-crisis or medication-stable periods, not just at worst. Mental illness claims are commonly denied when only crisis episodes are described; what passes is evidence of restriction present at least 90 percent of the time, including baseline periods. See our cumulative effects rule guide for the technical framework CRA reviewers apply, and our DTC denied appeal guide if a previous application was rejected.

Frequently Asked Questions