Rent that is never received does not have to count towards income indefinitely. Confirmation of the eviction order for non-payment marks the dividing line and opens the way to a tax credit.
For residential property, rent that is not received ceases to count towards income from the moment the eviction order for non-payment is confirmed, or a payment injunction is issued. This is an exception to the principle that income from land and buildings is taxed on an accruals basis, regardless of collection.
For taxes already paid on rent that accrued and was subsequently never collected, a tax credit is available equal to the tax paid on the rent not received, to be claimed once the failure to collect has been definitively established in the court proceedings.
The favourable regime presupposes a court order: until confirmation, the rent counts towards income. A distinction must also be drawn between residential leases and leases of business premises, which are governed by different rules. Orderly document management is decisive if you are not to pay tax on income never received.