A Codice Fiscale (or fiscal ID code) is a necessary component to almost all financial transactions in Italy. It's like an American social security number, but it seems even more important and is required as personal identification in most business transactions (opening a bank account, getting a phone line, etc). For example, we received a package from the post office and before they would let us pay the duty on it, we had to produce a Codice Fiscale. (Although they didn't seem to care whose codice fiscale it was - when we said we didn't have one yet, the post office told us to submit a friend's!)
But getting our Codice Fiscale (pronounced "koh-dee-chay fees-kah-lay", I believe) turned out to be simple - one of the easier parts of getting settled legally in Florence. To get our Codice Fiscale, I went to the Agenzia delle Entrate located at Via S. Caterina D'Alessandria #23. Note: There are different office locations serving residents of different areas - and you can check which is your local office on the Agenzia delle Entrate website.
Although I went by myself, I got a Codice Fiscale for both Jane and Alice (my daughters) and Anthony (my husband). I had been told that I could apply for the girls without them being present, but at first I thought they might want Anthony to apply in person. I don't know if it's policy or if they just made an exception for me - but they had a little conversation that I didn't understand, and then let me sign all four applications (probably because I had their passports and Permesso di Soggiorno).
The whole process went something like this: In the main entrance of the agenzia, there was a "Prima Informazione" desk where I picked up applications. When I had filled them out, I went to the ticket-issuing machine and pressed the green button for "Codice Fiscale". With my ticket in hand, I waited for the digital sign to call my letter/number. When called, I went to the appropriate "Sportello" (or window) and I turned in my applications, passports and Permesso di Soggiornos. Nearly instantly, I was issued a sheet of paper for each of us, with our individual Codice Fiscale.
Now I'm just waiting to get official cards in the mail, but I have these papers for identification in the meantime. Easy as 1-2-3 (1-application, 2-passport, 3-permesso di soggiorno)! Allora...