Land registry update: which building interventions require the income to be revised

An obligation that comes from afar

The resolution recalls, first of all, that pursuant to articles 173 and 204 of the royal decree-law of 13 April 1939, n. 652, the update of the annuity is always due in the presence of changes in the intended use, consistency, shape, modification of the construction, plant, typological or distribution characteristics.

On this factual basis, in the case of Superbonus interventions, the obligation to change always exists. To be entitled to the increased rate, in fact, it was necessary to carry out major structural interventions, and only in the presence of these was it possible to combine “minor” interventions such as the replacement of systems.

However, doubts have remained so far in reference only to plant-related interventions, and the resolution specifically addresses these, indicating the procedures to be followed to evaluate whether or not the expansion of the equipment leads to the obligation to change.

The cadastral relevance of the new plants

For systems only, the reference parameter is that indicated by circular no. 36/2013, issued for photovoltaic systems but applicable in general. Here it is specified that the obligation is triggered in the event of an increase in the profitability of the property by a threshold greater than 15%.

The circular specified that systems with a nominal power of no more than 3 kilowatts per property unit remained below the threshold, otherwise it was necessary to evaluate the intervention specifically. In fact, nowadays, considering the average power of the systems double compared to the past, the calculations become mandatory.

The calculation method

To verify whether the plant expansion exceeds the threshold of cadastral relevance, the resolution establishes the application of the same methods envisaged for properties with special and particular uses (circular no. 6/T of 30 November 2012), for the comparison between the cadastral value before and after the intervention. The calculation is structured as follows:

V_ante = Rc × M
V_post = V_ante + V_systems

Where:

• Rc is the cadastral income of the real estate unit in deeds before the intervention;
• M is the multiplier provided for by ministerial decree no. 5646 of 14 December 1991 for the cadastral category of the unit;
• V_impianti is the average inter-census value of the installed systems, referring to the two-year economic period 1988-1989.

The average inter-census value corresponds to the value of the systems reduced by the so-called inter-census depreciation, calculated according to the useful life and residual value of the plant component. In the absence of specific sector investigations, the resolution allows us to assume, as a first approximation, a useful life of 20 years and a residual value of zero at the end of the same.

The comparison between V_ante and V_post presupposes in any case a preliminary check: the classification in deeds must correspond to the actual state of the property prior to the intervention.

The drafting of Docfa declarations

The resolution also provides operational indications for cadastral update documents via the Docfa procedure. The technical report must include the following in an exhaustive manner: the description of the interventions carried out, the list of new systems installed and the relevant significant characteristics – with indication, for example, of the nominal power of the photovoltaic systems and storage systems.

A procedural criticality concerns cases in which the real estate unit, following the interventions, takes on the characteristics of a cadastral category or class not present in the tariff framework in force in the census area of ​​location. The Docfa procedure does not allow the direct indication of a different classification. In application of the art. 11, paragraph 2, of the legislative decree of 14 March 1988, n. 70, converted by law 13 May 1988, n. 154, the declaring party indicates in the technical report the category and class proposed, drawing them from the tariff framework of another census area of ​​the same municipality or another municipality of the same province. The determination of the definitive income remains in any case the responsibility of the relevant Provincial-Territorial Office.

The evaluation process

From Resolution 21/E of 2026, a three-step process can be obtained:

• The first is the verification of the classification in deeds: it must correspond to the state of the property before the intervention; if it does not match, you must first update to the previous state.
• The second is the classification of the nature of the intervention: if it involves a change in destination, consistency, shape or plan, the obligation to update is automatic; if it concerns a plant expansion in the strict sense, the V_ante/V_post comparison is applied with the 15% threshold.
• The third concerns mixed interventions, in which systems and building works are combined: in this case the technical-estimative evaluation must be overall and cannot make use of the simplified criterion.

Land registry relevance of building interventions: summary diagram

We see in this summary table the cadastral relevance of various building interventions, with the relative obligation (or non-obligation) of cadastral updating: