Once the NIF has been obtained, the company should be registered with the pertinent regional Mercantile Registry. This would usually de done through the notary once the relevant deeds have been prepared.
Resident companies and non-resident companies with a permanent establishment in Spain need to have notarized deeds setting out the articles of association and objectives of the company, together with details of the type of governing body and the names and powers of the company directors and officers. These deeds are required for any dealings with local authorities, banks, utility companies etc. The deeds need to be registered with the local Mercantile Registry.