The maintenance costs for condominiums or single-family houses quickly exceed the flat-rate deduction. Many tax-deductible costs are not always familiar to even investment officers. For example, the fees for water meters, the costs for heating service subscriptions or the effort involved in preparing heating bills. The authority then often deletes the entire deduction and only allows the flat-rate deduction. You can appeal against this.
You can find the deductible maintenance costs for properties in the Canton of Zurich at: To the Cantonal Tax Office in Zurich