The CRA may require a signed statement indicating the nature of the infirmity (mental or physical condition), when it began, and how long it’s expected to last, from your dependant’s healthcare practitioner. If the CRA already has an approved Form T2201, or Disability Tax Certificate on file for your dependant, you won’t be required to provide a statement.

When claiming Canada Caregiver for your spouse TurboTax will calculate this for you. 

CRA'S rules in claiming the Canada Caregiver Amount.