Unfortunately, the indices do not always constitute an organic, self-contained series, nor does such a series – when it exists – always appear complete, as it can happen that individual annual indices are placed before or at the end of the registers to which they refer. The indexes show for each person the deed number and the page of the civil status register for the reference year.

These indexes of Civil status registers were already provided for in the French legislation that introduced the Civil Status in Italy and, therefore, can be found in Napoleonic civil status archives and those of the Restoration. Even in the early years of the 19th century it could happen to find indexes compiled by name and not by surname.

However, with the Unitary Civil Status, indexes began to be compiled in a systematic manner: the law stipulated that the registers had to be closed at the end of each year with a written and signed declaration immediately after the last deed. After 1 January of the following year, the civil registrar of the municipality, in the relevant declaration, indicated the number of deeds entered in each register and formed, for both copies, a annual index in alphabetical order of the surnames of those to whom the deeds referred (Articles 29 and 30 of Royal Decree No. 2602 of 15 November 1865).

In addition to the annual index, the ten-year index was also compiled every decade in a double original. The indexes were to be compiled ‘in alphabetical order spelled out by surnames’ (as prescribed by the ministerial circular of 3 August 1874, which stipulated that the surname must always precede the first name).

In order to distinguish the acts in the second part of the registers from those in the first, the letter ‘S’ was placed next to the register and act number in the indexes.

As mentioned above, the annual and decennial indexes contained, in addition to the year, a reference to the number of the deed, thus enabling the document sought to be identified in the specific series (registers of births, marriages and deaths).

On the other hand, with regard to the acts contained in the series of Annexes or Marriage Processes (documents presented in the case of civil marriages), it is possible to retrieve them by referring to the act number of the promise of marriage together with the year.