Donating 5 for each 1000 is a small gesture that does not cost anything yet is fundamental for some children.

CODICE FISCALE
94252910487

5 x 100 is a fraction of IRPEF. It is absolutely not an additional expense.
If you decide not to give 5 x1000 to anyone, that part of IRPEF will still be paid to the State.

The models for the income tax return contain a space dedicated to the 5×1000, in the section related to the “support of voluntary work, of non-profit organisations of social utility,…” in which you can sign and indicate the tax code of the Smile Project association.