Learn Italian: Il testamento che ha redatto il notaio è legittimo. - The will that the notary drafted is legitimate.

In Italian relative clauses, it is very common to invert the word order and put the subject at the end. Saying che il notaio ha redatto is grammatically correct, but che ha redatto il notaio sounds more natural because it places the emphasis on the person who performed the action.

Redatto is an unusual past participle. What is its infinitive?

The infinitive is redigere, which means to draft, compile, or draw up a document. It is an irregular verb. You will often see it used in legal, formal, or administrative contexts, such as drafting a contract or a will.

Could we use cui or il quale instead of che in this sentence?

You cannot use cui because it must be preceded by a preposition (like di cui or a cui). While you could technically use il quale as the direct object, it sounds extremely formal and heavy. Che is by far the most natural choice here for a direct object relative pronoun.

Is a notaio exactly the same as a notary in English-speaking countries?

No, they are quite different. In Italy, a notaio is a highly specialized and prestigious public official who is required by law to draft and validate major legal documents, like wills, real estate purchases, and corporate charters. They hold much more legal weight than a standard notary public in the US or UK.