A thirteenth is near-universalCCNL
The thirteenth salary (tredicesima) is an extra month of pay that almost every employee in Italy receives — across the private and public sectors — because the national collective agreements (CCNL) provide for it. It builds up over the year, roughly one twelfth for each month worked, and is typically paid out in December.
So if you work a full year, the thirteenth is close to a full month’s pay; if you join or leave part-way through, it is prorated to the months you actually worked. The calculator above lets you set that.
Why the thirteenth is taxed in full
The thirteenth does not carry a special tax rate — but it does not get the monthly reliefs either. INPS contributions apply to it just like ordinary pay (9,19% for the employee). The difference is on the tax side: the monthly employment tax credits (detrazioni) that soften each regular payslip do not reduce the thirteenth, because they are already applied across the ordinary months.
With the credits absent, the IRPEF on the thirteenth is charged in full, at your marginal rate — which is why its take-home feels lower than an ordinary month even though the gross is the same. This is standard payroll practice, widely reported; it is flagged here as not confirmed against a primary Agenzia delle Entrate document, so treat the thirteenth’s figures as an estimate to check with your employer.
