DSU 2026: when to request it and how to file it without errors

What the DSU is, explained well

Denis is 34, works in a warehouse on via Fulvio Testi and in September he became a dad. At the town hall desk, while asking for the reduced nursery fee, he heard a new acronym: «you need the ISEE». His question is the same one that reaches us every week: «and how do you do the ISEE?». The answer is a single word: DSU.

The acronym stands for Dichiarazione Sostitutiva Unica (Single Substitute Declaration). It is the form with which you tell INPS what your family looks like: who lives in the household, how much it earned and how much it owns. With those numbers INPS calculates the ISEE, the score that public bodies read to understand whether you are entitled to help. Remember it like this: the DSU is the application you fill in, the ISEE is the answer you receive already calculated.

What counts inside the DSU 2026

2024: the snapshot from two years ago

Watch the year, because it is the detail that catches everyone out. The DSU filed in 2026 describes the family with the income received between 1 January and 31 December 2024 and with the assets held at 31 December 2024: not today's salary, but the one from two years ago. The 2024 income is proven with the Certificazione Unica 2025, or with a copy of the 730 or the Modello Redditi filed in 2025. The household, on the other hand, is the one that exists on the day you file the declaration: if a child is born in March or a child goes to live alone, the household changes immediately and the DSU has to be redone.

Validity: until 31 December 2026

The ISEE certificate that comes out of the DSU is valid from the day of filing until 31 December 2026, always and whatever happens. Whatever month you file it in, the expiry stays the same: whoever files in January and whoever files in November lose its value on the same day. To use it in 2027 you need a new declaration, because the year of the reference income changes.

The folder of documents

No panic and no piles of paper: one envelope with the right papers is enough, and the declaration is filled in together with the operator. Here is the list to check on the table before leaving home.

• identity document and tax code of every member of the household, children included
• stato di famiglia (household certificate), or the self-certification of the household composition
• Certificazione Unica 2025, or a copy of the 730 or the Modello Redditi filed in 2025
• certificates of exempt income, NASpI, benefits and maintenance payments received or paid in 2024
• balance at 31 December 2024 and 2024 average balance of current accounts, passbooks and prepaid cards
• value at 31 December 2024 of securities, savings bonds and redeemable life insurance policies
• cadastral records of properties and remaining principal of mortgages at 31 December 2024
• registered rental contract, if the home you live in is rented

The same sheet is almost always missing from the folder: the 2024 average balance certificate. Be careful not to confuse it with the year-end balance: banks and Poste issue on request the average of the daily balances of all of 2024, and that is the number you actually need. If you have accounts abroad, cryptocurrencies or company shares, tell the operator straight away: the DSU has dedicated sections and skipping them exposes the declaration to corrections.

Where to file the DSU: the three routes

The declaration is filed in three ways. The final result does not change: what changes is the minutes it takes you, the number of steps you do on your own and how easily a wrong figure slips into the case file.

1. At the patronato, at Via Oreste Terenghi 21/23

It is the route for those who want to close everything in one go. You reach us however you prefer — by phone, on WhatsApp or in person — you book the appointment and you come with your envelope of documents. The operator checks the papers, fills in the declaration together with you, shows it to you before sending and transmits it to INPS online. We are open Monday to Friday, from 9:30 to 12:30 and from 15:00 to 19:00, and we see people by appointment only. Filing the DSU is a paid service of our patronato: we tell you the amount before we start.

2. On your own, with the pre-filled DSU

With SPID, CIE or CNS you can use the Portale unico ISEE on the INPS website or the INPS Mobile app. The pre-filled version already contains the income and assets that the Agenzia delle Entrate and INPS hold on file: you check, correct and confirm. Since 1 January 2026 the pre-filled form has become the priority route even when you rely on a CAF, and the data also comes from the registry office and the public car register. The fact remains that every number has to be verified: some data, starting with current accounts, often has to be entered by hand.

3. At the Comune or the body that provides the benefit

The Comune and many bodies that pay out the benefit also collect the DSU: it is the convenient route when you submit the application directly at the desk you need. For households with several members, owned homes or slightly tangled situations, though, the sections to fill in become many and the risk of making a mistake grows.

Back to Denis: one Tuesday morning he arrived with his envelope, in forty minutes the DSU was transmitted and the nursery application went out the same day. «I thought I needed an accountant», he said as he drove home. You do not: you need the right papers and an hour of your time.

When to file it: the moments that matter

Like with the Post: it does not matter when you send it, it matters when it arrives. The DSU is filed at any time of the year, but the ISEE must already be valid when you submit the application for the benefit you need. Here are the moments when filing it late really costs you something.

• nurseries and school meals: the Comune's applications open in late spring, and those who already have the certificate in hand fill them in without rushing
• university fees and scholarships: every university has its own dates, and after the deadline fixed penalties apply to the ISEE filed late
• single allowance for children: without a valid ISEE, from March you stay at the minimum amount; those who filed the DSU by 30 June 2026 got the recalculation with arrears from March, while after that date the recalculation starts from the following month
• social bonuses on electricity, gas and waste, nursery bonus and concessions for the elderly and disabled: the ISEE must be updated every year, otherwise the benefit is interrupted
• changes in the family: the birth of a child, marriage, separation or a member moving out change the household and require a new declaration

A practical detail that avoids panic: the certificate normally arrives within the tenth working day from filing the DSU. It is not instant like a receipt, so a declaration made the week before the deadline is already late. The right habit is to count back two weeks from the date that matters to you and book with that margin.

If something changes or goes wrong: corrections and the current ISEE

Two surprises get solved at the office, never on your own. The first concerns mistakes: if the certificate contains wrong data or omissions, you file a correction with form FC.3, and INPS can in any case flag discrepancies between what was declared and what its archives show — one more reason to check every number before sending. The second concerns real life: if after filing you lose your job, end up on short-time work or have your hours halved, you are not stuck with an old number. With the current ISEE you update the declaration with the income of the last twelve months (or the last two months multiplied by six, if you lost or reduced a permanent job): you request it when the household income drops by more than 25% or your work situation changes, and since 1 April also when your assets change by more than 20%. Updating only the income makes it valid for six months; updating the assets too makes it valid until 31 December, and the change must be reported within two months.

The questions we get asked most

Here are the five answers we hear repeated most often at the desk. If your situation is different, call us or write to us on WhatsApp: we see people by appointment at Via Oreste Terenghi 21/23, in Cinisello Balsamo, Monday to Friday between 9:30-12:30 and 15:00-19:00.