ISA (indici sintetici affidabilità)

11/12/2025
The ISA, short for Indici Sintetici di Affidibilità Fiscale, are standardized questionnaires that companies and freelancers are required to submit as a mandatory part of their tax return. The main purpose of the ISA is to verify the credibility of the income declared by the taxpayer.

Structure and Calculation

Currently, there are 172 different questionnaires, with the correct choice depending on the specific business activity carried out. Regardless of the type of questionnaire, data from financial accounting as well as information on employed personnel (e.g., paid working days of employees) must always be provided. In addition, depending on the industry, specific activity-related data is collected (such as number of beds or charged rates for accommodation businesses).

Based on the entered data, the Revenue Agency’s software assigns a score on a scale from 1 to 10, with 10 being the best value. At the same time, the average score of the last two tax periods is calculated.

Impact of the ISA Score

The ISA score is decisive for tax reliefs or controls:

  • Advantages (score of at least 8 or a two-year average of at least 8.5):
    • Reduction of the statute of limitations for tax violations by one year.
    • Increase of the thresholds above which certification by a tax advisor is required for the offsetting of tax credits.
  • Disadvantages (score of 6 or lower):
    • The likelihood of a tax audit increases, especially if a low score is recorded over several tax periods.
  • Neutral (score above 6 and below 8):
    • Neither advantages nor disadvantages are foreseen.

Important Exceptions

In certain cases, the ISA questionnaire does not have to be completed. The main exceptions are:

  • Start-up or termination of the business activity during the tax period.
  • Revenues exceeding € 5.164.000 in the tax period.
  • Application of the flat-rate taxation regime during the tax period.
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