ISTAT rent update in Trieste: when, how much and how to ask

The ISTAT update of the rent is due only if the lease provides for it and you have not chosen the flat-rate tax (cedolare secca). On a 3+2 regulated rent (canone concordato) in Trieste you can ask for at most 75% of the change in the FOI index, which in September 2026 was 4.0% over one year: on €600 a month, at most €18 more.

Which index, and where do you find it?

The consumer price index for blue- and white-collar households (FOI) excluding tobacco, the one ISTAT indicates for rents. You find the 12-month change on the ISTAT page "Indice dei prezzi per le rivalutazioni monetarie", in the monthly release "Prezzi al consumo" or with Rivaluta, ISTAT's calculator.

Latest figure, from the release of 16 October 2026: in September 2026 the FOI excluding tobacco was 4.0% higher than a year earlier. It changes every month: read the one for your month.

A warning: since January 2026 the index has a new base (2025=100) and can no longer be compared directly with figures in old tables: use the published change.

Regulated rent in Trieste: how much and how?

The ministerial decree of 16 January 2017 allows territorial agreements to provide for it, only without the cedolare, up to 75% of the ISTAT change. The ministerial 3+2 model contains the clause, with a blank for the percentage: check yours.

Then it depends on which agreement your lease follows: for the Comune, two are in force.

• Agreement of 15/12/2025 (leases from 16/12/2025). Article 14: annual update from the second year, upon prior request by the landlord by raccomandata A/R or PEC, up to 75% of the FOI change over the previous year.
• Agreement of 14/12/2022, extended (earlier leases, and those certified by its organisations): rent "updated annually in the measure agreed by the parties", up to 75%.

The ministerial models for the temporary lease, which lasts at most 18 months, and for the student lease have no such clause: for a student lease longer than a year, ask the organisation that certifies it.

And on a free-market 4+4?

The clause decides. The 75% rule of the old fair-rent law (equo canone, article 24 of law 392/1978) was repealed for homes by law 431/1998; a similar cap remains for shops and offices (article 32).

If the lease does not provide for it, there is no update: an increase outside the written and registered lease is void (article 13 of law 431/1998).

Is it possible with the cedolare secca?

No. For the whole period of the option the right to ask for an update is suspended, ISTAT included, even if the lease provides for it. The rule cannot be waived: today it sits in article 3 of legislative decree 23/2011, from 2027 in article 206 of legislative decree 117/2026. Circular 26/E of 2011 from the Agenzia delle Entrate adds:

• in co-ownership, if even one owner opts, the waiver applies to the whole lease;
• you can revoke the cedolare in a later contract year, within 30 days of the end of the previous one, paying the registration tax; but if you leave it from the second year, the second year's update is lost.

Is it worth giving up the cedolare for ISTAT? On a regulated rent, hardly ever. With €600 a month and the index at +4.0%, the update at 75% is worth €216 a year gross. Without the cedolare you pay IRPEF on 66.5% of the rent (95%, cut by a further 30%): at 33% that is €1,580 against €720 under the 10% cedolare, €860 more, not counting surcharges and registration tax. At 23%, €381 more.

How do you ask?

By raccomandata A/R or PEC: under the 2025 agreement it is mandatory, otherwise it gives you proof of the date. Include the lease details and registration code, the clause, the index month and the ISTAT change, the calculation, the new rent and the month from which you ask for it.

From when does it apply? The 2025 agreement does not say. The old fair-rent rule, "from the following month" after the registered letter, has been repealed for homes; the prudent choice is still to ask for the new rent from the month after the letter.

Can you claim arrears?

Under the 2025 agreement the update is "upon prior request", and article 14 refers to the change "over the previous year". If you have skipped several years, ask the organisation that certified the lease.

If you did ask and the tenant kept paying the old rent, the differences are rent and become time-barred after 5 years (article 2948 of the civil code).

And the registration tax?

Without the cedolare, if you pay year by year, the tax (imposta di registro) for each contract year is calculated on the updated rent and paid within 30 days of the end of the previous one, tax code 1501. On a 3+2 regulated rent the base is 70% of the rent. Under the cedolare there is no registration tax.

An example: a 3+2 at €600 from 1 October 2025

Assumptions: 3+2 regulated rent at €600 a month, signed and started on 1 October 2025, so under the 2022 agreement; update clause at 75%; no cedolare.

1. Index: FOI excluding tobacco, September 2026 on September 2025: +4.0%.
2. Percentage: 75% × 4.0% = 3.0%.
3. Increase: 600 × 3.0% = €18.00; new rent €618.00 a month.
4. Start date: on 20 October 2026 you send the PEC and ask for the new rent from November. In the second contract year you collect 600 + 11 × 618 = €7,398, €198 more; from the third, €7,416 a year.
5. Registration tax for the second year: 2% of 70% of €7,398 is €103.57, rounded to €104, split with the tenant.

Lease by lease

• Possible?if providedMaximumthe clause

  Free-market 4+4

  How: as the clause says

• Possible?from the second yearMaximum75% FOI

  3+2, 2025 agreement

  How: raccomandata A/R or PEC

• Possible?if providedMaximum75% FOI

  3+2, 2022 agreement

  How: as the clause says

• Possible?no, model without clause

  Temporary

• Possible?model without clause

  Students

  How: ask the certifying organisation

• Possible?no, for the whole option

  Under cedolare

  How: revoke it first