The Income Tax Return is a document in which every person who is resident in Italy declares his/her own income and calculates the eventual taxes due to the Italian state.
The document includes all types of income (work, pension, land, capital, buildings, businesses etc...) made in the previous year. Therefore, in 2016, you present your income for 2015.
Se non si presenta la dichiarazione dei redditi, avendone l’obbligo, si incorre in un illecito amministrativo, sanzionato.
If you do not submit your Income Tax Return Statement, which is obligatory, you will incur a sanctioned administrative offence.