Since January 1, 2026, under D.Lgs. March 14, 2025, no. 43 and the Ministerial Decree of March 10, 2026, the AD-1 declaration is no longer annual but semi-annual. Every power plant operator with a license or authorization from the Italian Customs Agency (ADM) must now file two declarations per year: the first covers January-June (H1) and is due by September 30, the second covers July-December (H2) and is due by March 31 of the following year. At the same time, the old system of fixed advance payments has been replaced by monthly payments calculated on quantities actually consumed or billed in the previous month and due by the end of the following month. For a full overview of AD-1 obligations under the new rules, see the complete guide to the AD-1 declaration.
Quick definitions
- Semi-annual cadence
- The filing frequency for AD-1 declarations from 2026 onwards; H1 covers January-June, H2 covers July-December.
- H1 2026
- First half of the year; meter readings required as of June 30, 2026; declaration due by September 30, 2026.
- H2 2026
- Second half of the year; data as of December 31, 2026; declaration due by March 31, 2027.
- Monthly down payment
- Electricity excise payment due by the end of the following month, calculated on actual consumption (or billing) for the previous month.
- True-up (conguaglio)
- The balance between the excise actually declared for the half-year and the monthly down payments already made in that period.
- Power plant (officina elettrica)
- An installation subject to an ADM license or authorization that produces, transforms, or distributes electricity liable to excise duty.
- D.Lgs. 43/2025
- Legislative decree that reformed the electricity excise rules in the Italian Excise Code (TUA), in force since January 1, 2026.
- DM March 10, 2026
- Implementing ministerial decree (Official Gazette no. 66, 03/20/2026) that sets the operating rules for semi-annual declarations, monthly payments, and the 15% bond.
From annual to semi-annual: what changed
Until 2025, the AD-1 declaration followed the calendar year: a single document summarized all excise-liable electricity consumption for the full year and had to be submitted to ADM by March 31 of the following year. Simple in design, but it left a gap of more than twelve months between the end of the tax period and the final settlement.
D.Lgs. 43/2025 cut that gap in half. Starting in 2026, each year generates two declarations, each with its own deadline:
| Half-year | Reference period | Deadline |
|---|---|---|
| H1 2026 | January 1 - June 30, 2026 | September 30, 2026 |
| H2 2026 | July 1 - December 31, 2026 | March 31, 2027 |
| H1 2027 | January 1 - June 30, 2027 | September 30, 2027 |
The filing workload doubles. The H1 deadline falls in mid-summer: operators without automated reminders or a structured management system risk missing the September 30 cutoff. In practice, a meter reading on June 30 of each year is essential to close out first-half data cleanly, on top of the usual year-end reading.
The transitional rule: the last annual declaration (year 2025)
The switch to semi-annual filing did not eliminate the obligation for the prior year. The declaration for year 2025 remained subject to the old annual rules: it was due by March 31, 2026 using the pre-reform AD-1 form.
The new semi-annual regime therefore applies starting January 1, 2026: the first semi-annual declaration covers H1 2026 (January-June) and is due September 30, 2026. Operators who filed their 2025 declaration on time are caught up; those who did not remain exposed to the penalties set out in the TUA.
Monthly down payments: how they work in 2026
The reform also overhauled the in-year payment mechanism. The old system required fixed monthly advance payments based on the prior year's tax liability, with a final true-up at the annual declaration. Predictable, but disconnected from actual consumption.
Starting January 1, 2026, the monthly payment is calculated on the quantities actually consumed (or billed) in the previous month and is due by the end of the following month:
- Self-consumption producers: excise on quantities self-consumed in the previous month.
- Sellers: excise on quantities billed to end customers in the previous calendar month, broken down by territory.
- Consumer-sellers: the sum of the two criteria above.
The true-up settled in the semi-annual declaration covers only the difference between monthly payments already made and the amount actually due for the half-year. For January 2026, a transitional rule applied: the payment due was equal to the December 2025 installment calculated under the old method.
Who is affected: the declarant categories
The semi-annual AD-1 filing requirement applies to every operator of a power plant holding an ADM license or authorization. D.Lgs. 43/2025 redefined the categories of obligated parties in Arts. 52-54 TUA. The main declarant categories are:
- Self-consumption electricity producers (commercial solar PV, cogeneration plants, hydroelectric installations)
- Electricity sellers to end customers
- Renewable energy communities (CER) that distribute energy to their members
- Wholesalers and intermediaries that buy electricity for resale
- Operators of local distribution networks
Plants generating electricity from renewable sources with a rated output below 20 kW, where all the energy is self-consumed by the producer, remain exempt from the filing requirement. For a full breakdown of all 8 declarant categories and their associated AD-1 sections, see the page on declarant categories and ADM obligations.
What changes in the AD-1 form itself
The AD-1 form has been updated to fit the semi-annual cadence. The main differences from the old annual form:
- The “reference period” field now shows H1 or H2 (no longer the calendar year).
- Section P (advance payments) has been reworked: payments are no longer calculated on a lump-sum basis; they match the monthly payments already made during the half-year.
- Any true-up amount resulting from the declaration is due by the filing deadline (September 30 for H1, March 31 for H2).
- Meter data must reference June 30 (H1) or December 31 (H2).
The updated form and the transmission specifications for 2026 were previewed in ADM Circular 34/2025 and formalized by ADM Determination 213396 of April 8, 2026.
Legislative sources
- D.Lgs. March 14, 2025, no. 43 - TUA reform, Art. 5 (semi-annual cadence)
- DM March 10, 2026 - Official Gazette, General Series no. 66, 03/20/2026 (prot. 26A01335) - Arts. 7, 8, 9 (monthly payments, semi-annual declaration, true-up)
- ADM Circular 34/2025 (December 2025) - filing instructions for the 2025 AD-1 declaration and preview of the 2026 regime
- ADM Determination 213396 of April 8, 2026 - updated AD-1 form and technical transmission specifications
Further reading
- Complete guide to the AD-1 declaration: sections, deadlines, and excise calculation - the full guide to the AD-1 declaration under the new rules.
- D.Lgs. 43/2025: complete guide to Italy's electricity excise reform 2026 - the reform that introduced semi-annual filing and every other change.
- DM March 10, 2026: the implementing decree for electricity excise - the implementing decree covering monthly payments, true-up, and the 15% bond.
- Power plant declarant categories, ADM licenses, and obligations - the 8 declarant categories and their semi-annual deadlines.