Italian Thirteenth-Month Pay Calculator
Work out the gross tredicesima you have accrued and what reaches your account: the twelfths, the INPS contributions and IRPEF at the right bracket, without the tax credits that do not apply to a tredicesima.
Normally 9.19% as your share (10.19% above €56,224 a year). The surcharges are usually not withheld on the tredicesima: leave them at 0 for the payslip net.
You have accrued 12 twelfths out of 12. The tredicesima is taxed at your 23% marginal IRPEF rate with no employment tax credits applied, so 30.08% of the gross is withheld in total.
How the result is reached
| Gross tredicesima accrued | €2,000.00 |
| INPS contributions (9.19%) | −€183.80 |
| Taxable amount | €1,816.20 |
| IRPEF (23%, no tax credits) | −€417.73 |
| Estimated net tredicesima | €1,398.47 |
The IRPEF is worked out as the difference between the tax on the annual income with and without the tredicesima, so a bracket crossed halfway is not taxed entirely at one rate. The taxable income from the ordinary payslips used as the base is €21,794.40, which places the tredicesima in the 23% bracket.
The employee share is the pension (IVS) share of the Fondo Pensioni Lavoratori Dipendenti, Italy's main employee pension fund: 9.19%, with the employer carrying the other 23.81%. Above €56,224 of annual pay a further 1% applies, so enter 10.19 in that case. Apprentices and some sectors pay different rates, and the exact figure is on your payslip. The regional and municipal surcharges almost never appear on the tredicesima payslip, because they are settled against the annual total and withheld in instalments: leave them at 0 to see what actually arrives, or enter your combined rate to estimate the full-year cost.
Educational estimate, not tax or employment advice. Which pay elements count towards the tredicesima, and how an incomplete month is counted, are set by your CCNL (the sector collective agreement); the exact net also depends on the tax credits and surcharges applied on your payslip. Check with your payroll adviser or HR department.
One twelfth for every month worked
The tredicesima accrues in twelfths: each month of service in the year is worth one twelfth of your gross monthly pay. A full year accrues 12 twelfths, which is one whole month of pay; starting in June accrues 7. The formula is monthly pay × months of service ÷ 12. If you work part time, enter the pay shown on your payslip: it is already proportional to your contracted hours, so no extra percentage is needed.
The 15-day rule for an incomplete month
When you are hired or leave mid-month, that month counts in full if you worked at least 15 days, and not at all below that. It is a hard threshold rather than a proportion: 14 days accrue nothing for the month, 15 days accrue a whole twelfth. This is the convention most CCNLs (the sector collective agreements) use, but a minority prorate by day instead (days ÷ 30). The calculator lets you choose, because the gap for that month is the entire twelfth.
Which months accrue and which do not
Periods where the employment relationship is live and either paid or protected accrue: holiday, paid leave, sickness within the contractual limit, injury and compulsory maternity leave. Unpaid leave, strike days, optional parental leave and unjustified absence generally do not. The exact list is set by your CCNL, so the calculator asks for the months you actually accrued rather than guessing them for you.
Why the net tredicesima is lower than a normal payslip
The difference is not the rate, it is a missing tax credit. The tredicesima pays INPS contributions like any other pay (normally 9.19% as your share) and IRPEF at the same rates as any other month, but the employment tax credits, those for dependent family members and the trattamento integrativo are already spread across the twelve ordinary payslips and are not granted a second time on the extra one. That is why a gross of €2,000 nets around €1,400, while an ordinary payslip of the same amount leaves more.
IRPEF at the right bracket, even halfway through one
For 2026 the IRPEF rates are 23% up to €28,000, 33% between €28,000 and €50,000 and 43% above (the second one fell from 35% to 33% with the 2026 budget law). The tredicesima is added to the year's income, so it can land across a bracket boundary: rather than applying a single rate to the whole amount, the calculator computes the tax on the annual income with and without the tredicesima and takes the difference. For an income that crosses €28,000 precisely because of the tredicesima, that is the only way to get the right figure.
The regional and municipal surcharges come later
The tredicesima payslip usually shows no regional or municipal surcharge: those are computed on the annual total at the year-end reconciliation and withheld in instalments over the following months. The tredicesima does enter that base, so the surcharge on it is paid, just later. Leave the field at 0 to see what arrives in December, or enter your combined rate to estimate the full-year cost.
Worked example
Example: you earn €2,000 gross a month and worked the whole year. You accrue 12 twelfths, so a gross tredicesima of €2,000. INPS contributions at 9.19% are €183.80, leaving a taxable amount of €1,816.20. Your annual taxable income from the ordinary payslips is €21,794.40, inside the first bracket, so the IRPEF on the tredicesima is 23% of €1,816.20, or €417.73. The estimated net is €1,398.47, which is 30.08% less than the gross. At €2,500 a month the calculation changes character: the ordinary income stays under €28,000 but the tredicesima pushes past it, so part is taxed at 23% and the rest at 33%, giving €673.48 of IRPEF and a net of €1,596.77.
Frequently asked questions
How do you calculate the tredicesima?
When is the tredicesima paid?
How much of the tredicesima goes in tax?
Is the tredicesima taxed more heavily than salary?
If I only worked 10 days in a month, does that month count?
Does the tredicesima accrue during sickness or maternity leave?
Is the tredicesima reduced for part-time work?
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Sources
- Presidential Decree 1070/1960 (with the interconfederal agreement of 27 October 1946) · Normattiva, Istituto Poligrafico e Zecca dello Stato
- IRPEF rates and how the tax is calculated · Agenzia delle Entrate
- Law 199 of 30 December 2025 (2026 budget), art. 2: second IRPEF rate cut to 33% · Normattiva, Istituto Poligrafico e Zecca dello Stato
- Presidential Decree 917/1986 (TUIR), art. 11 and art. 13 · Normattiva, Istituto Poligrafico e Zecca dello Stato
Author: Thorben Rasmus Idel · Reviewed by: Nahar Geva · Last reviewed: