For the Chamber of Deputies, Italy is divided in 26 constituencies. Political parties are submitting lists of candidates and may also form coalitions. In order to stand for election to the position of ruling party, they are obliged to submit their manifesto and announce their leader.
The statutory minimums of threshold differ between the single parties and the coalitions. A minimum of 4% is required for a single party and a minimum of 10% is required for a coalition. Within these coalitions, the lists obtaining 2% of the valid votes cast shall be admitted to the distribution of seats (if the lists fail to win 2%, seats are given to the list with the highest number of votes). The linguistic minorities between the coalitions of lists shall obtain at least 20% in their constituency. A number of “topping-up” bonus seats are given in the coalition, or the single party, which obtain plurality, in order to reach 340 seats. The candidates are elected in each constituency according to their position in the list.
The electoral system for the Senate of the Republic is regional-based. The constituencies are divided in the 20 regions of Italy and another 6 Senators are elected from the Italians living abroad. The thresholds are a minimum of 20% for a coalition and a minimum of 8% for a single party. Within the coalition, any party shall obtain 3% of the valid votes cast, without priming the first party and there no guaranteed majority for the larger party.
Sources: Italian Ministry of Interior, Wikipedia