The sums for which the application of withholding taxes is predicted, are subject to single certification, referring to:

- income from self-employment;

- commissions, however, denominated for services, even occasional, relating to commission, agency, brokerage, trade representation and business procurement relationships;

- different incomes, such as occasional self-employment income, income from non-routine commercial activities, proceeds from copyright, income deriving from the assumption of obligations to do, not to do or to allow.

It should be noted that the same income categories, in the event that the recipients have opted for the benefit scheme for youth entrepreneurship and the mobile workers, referred to in Article 27 of the Legislative Decree n. 98/2011 (c.d. "Minimum tax payers") or for the flat-rate scheme, as per article 1, paragraphs 54 to 89, of Law no. 190/2014 and subsequent amendments, although not subject to withholding taxes, are subject to single certification.