My expertise is with the former Papal States and the former Kingdom of the Two Sicily’s so this information may not apply to Northern Italian civil records.
First a little history. In 1809 Napoleon conquered Italy and ordered the keeping of civil records for births, marriages and deaths. The format was the same as that used in France. In 1815 when Napoleon was defeated the Kingdom of the Two Sicily’s continued the keeping of civil records. In the Papal States, many towns destroyed the 6 years of records they had made and reverted to the church keeping records as before. Between 1860 and 1870 in various parts of the country towns began once again to keep civil records using the Napoleonic format. Between 1809 and 1865 the Kingdom of the Two Sicily’s had been making TWO copies of its records and sending one copy to the State. After 1865 this practice ceased in most areas and the towns made just one copy which they kept. After 1866 notations were made on the birth records of marriage, death and even divorce dates. In some towns these notations were also made on the second copy which was eventually sent to the State Archives. Wars, earthquakes and other natural causes have resulted in towns losing their civil records. Where this happened the TRIBUNAL assisted in reconstructing the lost records. The people still alive went to the Tribunal and made statements under oath which were then accepted as official. When consulting reconstructed records remember that people often went and reconstructed only the records that were needed. Marriage records may not have been reconstructed and almost certainly deaths that had already occurred were not. Residents who had emigrated usually did not reconstruct their birth records unless they needed to for some reason.
The Mormon Church went to Italy and negotiated with the State Archives to microfilm their copies of the country’s civil records. They did not go town to town although they may have filmed in some major towns. Not all the State Archives agreed to allow filming, notably Rome, Salerno and Florence among others. In the towns under the rule of the Papal States you may find many years missing, just because they were not filmed doesn’t mean they don’t exist. The town almost certainly has their copy. If there are no notations on the film copy, the town may have them on their copy.
One last thing: If you are searching in the Papal States you should know that there was some resistance by the population to the return to civil record keeping in 1870 and although they complied with birth and death registration they did not always comply with the registration of their marriage. The towns had a unique way of forcing compliance. When a child was presented for registration of birth by the father, the child received the father’s surname but if the couple were not married civilly the mother’s name was not recorded. If the midwife presented the child often neither parent’s names were recorded and the child was given an invented surname and registered as ‘unknown parents’ (genitori ignoti). If the mother presented the child, it would be given her surname and the father’s name was not recorded. Years later when a birth certificate was needed for school or marriage and the illegitimate status was revealed, the couple would do the civil marriage and register the names of all their living children thus legitimizing them. These names and birth dates can be found on the marriage record. The children’s birth records were then corrected and a notation made to this effect.
The microfilms are a valuable resource for researching Italian records but remember, you are only searching 2nd copies.