The interest rate on the last month’s rent deposit is the same rate as the rent increase guideline. However, interest on the last month’s rent is paid annually and according to the rent increase guideline of the year in question. Based on this scenario, you owe the interest on the last month’s rent deposit for two years. Assuming the tenant moved in March 2016, you would pay the interest for the first year in March 2017 according to the rent increase guideline of 2017. You would then pay the interest for the second year in March 2018 according to the rent increase of 2018. You can find the interest rates for the past few years on our website at https://www.landlordselfhelp.com/RentIncreaseGuideline.htm or at https://www.ontario.ca/page/rent-increase-guideline.