A private deal needs a public signature
Two firms can sign whatever they agree. That is the point of a private deal, and it is also the problem. Nothing on the page ties it to an office of the state, and state desks only sign off signatures they can trace. So the first step is to give them one they can.
The notary, and then the court
A notary watches the signing and certifies each signature. Once he has done that, the page counts as a notarial paper, and notarial papers are signed off by the Procura della Repubblica, the prosecutor's office housed at the court. Office and town hall papers go to the Prefettura instead, which is why the two addresses get confused.
Get both sides signed if you can. Where the other company signs elsewhere, ask whether their signature is being certified too, because some receiving offices want every name on the page traceable. That is the practical answer to how you legalize a commercial contract without a second trip: settle the signatures first.
Annexes, price lists and page order
A deal is rarely one sheet. Schedules, price lists, maps and specifications ride with it, and the stamps apply to the bundle as it was bound. Never open the file to add a sheet afterwards. If a schedule is missing, bind it in before the notary sees the deal, or you will pay for the chain twice.
Number the pages and initial them if your lawyer advises it. Then, when you legalize a commercial contract in Bari, the clerk finds a file that cannot be argued with: fixed order, fixed count, one signature block, one seal. Files that arrive loose in a folder are the ones handed back.
The consulate, the fee and the wait
After the court's desk comes the last link, where the embassy legalization of a commercial contract in Bari is completed at the other country's embassy or consulate in Italy. Whether that link is needed at all turns on where the deal will be used, so ask the receiving authority in writing and keep what they send back.
Costs are simple to plan. A €16 tax stamp, the marca da bollo from any tobacconist, covers the Italian side; the consulate sets its own fee and may price by sheet. Consular legalization of a commercial contract in Italy usually takes 10–15 business days, or 3–5 business days on a faster slot.
Where these files end up
Tender boards, ministries, agency registers and courts all ask for stamped deals. An embassy attestation of a commercial contract in Bari may also be wanted before a distributor can be recorded as yours, or before a payment can be released. Ask which body will hold the file, because that body sets the rules everyone else follows.