Service oriented architectures offer a fast and easy deployment method to add new functionalities to existing applications. In particular, digital signature generation and validation web services, offered in this site, can be used into the processing of commonly used formats of electronic invoices.

What is an electronic invoice?

The electronic invoice is the cfwommercial document, in electronic format, that has the same value of its paper predecessor. This invoice management system allows issuer and receiver to reduce costs and streamline associated processes. Several studies estimate savings greater than 70% (labor force, paper, stamps, etc.)

European Union currently valid legal framework, specifies the minimum technical and legal requirements to be met. One of the most important ones is that electronic invoice must guaranty the authenticity and integrity of the enclosed data. The use of advanced electronic signature is one of the alternatives to satisfy this requirement: Council Directive 2001/115/EC on VAT Invoicing to simplify, modernize and harmonize the requirements imposed to invoicing regarding the Value Added Tax.

The Spanish Goverment offers a compilation of legal norms in rule for Spain as well as the list of “valid certificates for electronic invoicing“, which are the majority of the existing issuers.

Electronic invoicing deployment

The above mentioned legal framework leaves to issuer the election of the technology to meet the technical requirements. Therefore it is possible to use PKCS#7/CMS, SMIME, or XML-DSig as digital signature formats, and Adobe’s PDF among others, EDIFACT or XML to represent the invoice. The last one is specially suitable for massive invoicing processes.

Companies with a higher volume of invoicing (issued or received) will need to adopt automatic mechanisms in their accounting systems. Providers of big companies will, as well, be drawn to issue invoices in the formats accepted by their customers. That leads to think of systems capable to adapt to the receiver’s needs.

Next figure describes the deployment of a generic system to issue and validate electronic invoices, with ability to recognize different formats.



The ERP system delivers the invoices which are signed prior to be sent to customers. Companies receiving high amounts of invoices will validate them prior to being automatically entered in their ERP system.

TrustedX platform allows to include suitable mechanisms to mechanize the creation and validation of electronic invoices. Electronic signature and verification services offered can deal PKCS#7, CMS/CAdES, S/MIME or even XMLDsig/XAdES digital signature formats which offers complete interoperability with current and future customers and providers.

Interoperability and standardization

At European level, CEN (European Committee for Standardization) tries to provide specifications to simplify e-business processes. Last July 2006 they created a document CWA 15579:2006 to help implementing and integrating hardware and software solutions to sign and verify e-invoices satisfying legal requirements.

The Spanish Tax Agency in cooperation with the Centre for Inter-bank Cooperation, representing the financial sector of the country, have established an XML based e-invoice format that we will refer as AEAT-CCI. The AEAT-CCI format contemplates the use of enveloped XAdES digital signature in two formats: a basic advanced electronic signature format (XAdES-EPES) and an advanced electronic signature format with validation information (XAdES-C).

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