An invoice starts as your own paper
You write the invoice, you print it, and no public office keeps a copy. That is the whole problem. A clerk abroad has no way to tell your sheet from one typed by anyone else. So the first job is not the stamp at all: it is getting a signature onto the page that an Italian office already knows.
Because of that, how to apostille a Commercial Invoice is really a question about the step before. Choose the wrong first step and the counter will turn you away, even though your paperwork looks tidy. Ask the buyer what they need in writing, then work backwards from their answer. That order of doing things is what keeps a shipment moving.
Two ways to make the sheet official
The common route is the Chamber of Commerce, which can certify a trade paper for use abroad. Its certificate is an administrative act, so the Prefettura, the state office for the province, adds the stamp on top. If instead an officer of your firm signs a declaration about the invoice in front of a notary, the paper becomes a notarial act, and the Procura della Repubblica at the court handles it.
Both routes work, and the difference is who is vouching for what. To apostille a Commercial Invoice in Genoa the office that signed first must belong to that province, because the clerk matches the seal against a local sample. Split the two across cities and you split the job, so keep the chamber, the notary and the court in one place where you can.
Fee and timing
The apostille cost for a Commercial Invoice in Genoa is a €16 tax stamp per document, and some documents are exempt. Whether a set of sheets counts as one paper is the clerk's call, so ask before you buy stamps. The queue at each office sets the pace, and a shipment date will not move it. File early in the week when a vessel is waiting.
Where a stamped invoice is used
Banks call for one under a letter of credit, brokers put it in a clearance file, and public buyers want it inside a tender. Some tax offices abroad ask for it when a firm claims money back on a purchase. Italy has been in the Hague Apostille Convention since 1978, so its member states take the single stamp and look no further.
Language and the details that get files sent back
Most export invoices are already in English, which the reader abroad usually prefers. Where yours is only in Italian, add a translation, and ask whether it must be sworn before a Tribunale, an Italian court, so the wording counts as accurate. The rules to apostille a Commercial Invoice in Italy sit the same in every province, but each customs desk reads its own way.
Check the firm names, the tax codes, the shipment marks and the goods description against the transport papers before you file. A single mismatch is enough for a broker to stop the clearance. The legalisation of a Commercial Invoice in Genoa for a country outside the Hague list goes through more offices, so ask your buyer early which chain their customs expects.