The tenant is required to give you a proper notice if they intend to vacate. They have not complied with notice requirements by simply stating that they do not intend to renew the lease. If the tenant moves out without providing the proper notice, the landlord is obligated to mitigate their losses and re-rent the unit as soon as possible.   As of September 1, 2021, landlords can file an application for loss of rent that the landlord incurred with the LTB up to one year after the tenant moves out of the rental unit. The tenant must have moved out of the rental unit on or after September 1, 2021. However, in order to file this application with the LTB, you will have to find out their new residential address to be able to serve them. The prescribed form is available on the LTB website at https://tribunalsontario.ca/ltb/forms/.