Medical expenses can be claimed for any 12 month period ENDING in the current tax year (and not claimed in the prior tax year). Generally, all eligible medial expenses can be claimed, even if they were incurred outside of Canada. When medical expenses are reimbursed by an insurance plan, only the portion not reimbursed can be claimed.
Only expenses in excess of the lessor of $2397(for 2020) of 3% of net income can be claimed. The lowest tax rate is applied to the medical expenses to determine the amount of the tax credit.