Final answer:
During months when a rental property is deemed substandard in California, the deduction for depreciation would be disallowed, while deductions for insurance, supplies, and utilities would generally still be allowable as operational expenses.
Step-by-step explanation:
The question pertains to disallowed deductions for rental properties on the California tax return. Specifically, during months when a property is deemed to be substandard, depreciation is the deduction that would be disallowed. This is because depreciation is a deduction that assumes the property is contributing to the production of income and in good condition. Therefore, if a property is substandard, it might not be considered as being used in a manner that justifies this depreciation deduction.
Other deductions like insurance, supplies, and utilities are generally considered operational expenses and would not automatically be disallowed just because the property is considered substandard. They are necessary for the maintenance and attempt to bring the property back up to standard, hence likely still deductible.