An invoice starts as a private sheet
An invoice starts life as your own paper. You typed it, you signed it, and no public office has touched it yet. That is why the chain begins with someone vouching for the signature rather than with a state stamp. Knowing how to legalize a Commercial Invoice means knowing that first link.
Getting the signature vouched for
A notary, or the body that keeps your company's record, can certify who signed. The point is narrow: the person named really holds that post and really wrote that name. Nobody at this stage looks at your prices or your goods. Once the signature is vouched for, you can legalize a Commercial Invoice in Florence through the state route.
Which state office stamps it
The Prefettura is the state's office in each province and it stamps administrative papers. Where a notary signed the certificate instead, the Procura della Repubblica at the court takes it, since notarial acts are its work. Ask which of the two your certificate falls under before you queue, because the desks do not forward files.
Make the sheet match the shipment
Customs officers read the stamped sheet against the goods. If the invoice says one crate and the packing list says two, the file stalls at the border and the stamps do not help. Check the totals, the buyer's name and the port before anything is stamped. The embassy legalization of a Commercial Invoice in Florence cannot fix a typo.
Cost and clock
The state side costs a €16 tax stamp — a marca da bollo from any tobacconist. The buyer's mission adds a fee of its own, and some set it as a slice of the invoice total. Allow 10–15 business days, or 3–5 if you pay for speed. Ask for the mission's fee in writing, because a slice of a large invoice can bite.
The buyer's mission here in Italy
The last stamp comes from the consulate or embassy of the buyer's country here in Italy. Bring the sealed sheet, the fee and any form the mission publishes. Some want a covering letter on your company paper too. The embassy attestation of a Commercial Invoice in Florence is what the buyer's bank or customs broker looks for.
When the chain is shorter than you fear
Not every destination asks for the whole run. Whether the consular step applies depends on the country the goods are going to, so confirm it with the receiving authority in writing. Some accept a single-step certification and let the rest go. The consular legalization of a Commercial Invoice in Italy is worth checking before you budget for it.