You can use ReFile in TurboTax or you can use the Canada Revenue Agency (CRA)’s My Account service to add your employment expenses to your 2022 return. This TurboTax FAQ has more information on changing a filed return: https://turbotax.community.intuit.ca/community/tax-return-amendment/help/i-have-filed-my-tax-return-...
You would need to ask your HR department for a T2200s or a T2200 for 2022 to claim your actual expenses. But, if they are not able to provide you with those forms, you can still claim the flat rate for work from home expenses.
