Gary owns a commercial building and leased his premises to John to conduct a bakery business. Under the lease contract, John is obliged to repair any modified or damaged parts of the building after the lease term. However, John fails to repair Garys building, which was damaged due to machinery and fixtures instalments. John agreed to pay Gary $3,100 to cover the repair expenses.

Required: With reference to relevant legislation and case law discuss the tax treatment of this payment for Gary. (10 marks, maximum 300 words)