Digital signature requirements in Portugal

In the fiscalization terms, a digital signature is obligatory for the invoices (receipts), equivalent documents (working documents), transportation or delivery notes, or any other documents which function as transportation documents and any other documents, irrespective of their designation, susceptible of being submitted to a customer to confirm the goods delivery or services.

From the technical point of the view, it is generated through the RSA algorithm based on the following information:

• Date of issuing
• Date and time of the last alteration of the document
• Receipt number
• Total of the receipt (rounded to 2 decimals)
• The signature generated in the previous document, of the same series
• and on the private key of the computer invoicing program producer

It is important to state, that a digital signature needs to be recorded in the invoicing database (which cannot be encrypted), and is directly associated with the original document’s record. Also, the version of the private key (sequential integers) that was used to generate the signature of the respective document needs to be recorded.