From Written to Electronic Form
A contract, as a bilateral legal act, represents a fundamental institution of legal transactions and a key mechanism for regulating relations between natural and legal persons. Its essence lies in the concurrence of wills, that is, the declaration of two or more parties to produce certain legal effects. Such consent may be expressed in different forms, and under the general rule of the Law on Obligations of the Republic of Serbia, the conclusion of a contract does not require a specific form unless otherwise prescribed by law.
In practice, the written form is most frequently used—either due to a statutory requirement (e.g., contracts concerning real estate transactions) or for evidentiary and protective purposes. However, as legal transactions become increasingly digital and accelerated, the traditional written form is often replaced by the electronic form as a modern means of expressing and recording legal declarations.
The electronic form allows a legal act to exist and be accessible in a digital rather than physical format. Based on this concept, the term electronic document has developed—an individualized digital record containing specific legal content such as a contract, statement, or invoice. Nevertheless, for an electronic document to have the same (or comparable) legal validity and evidentiary value as a handwritten document, it must contain an electronic signature.
The electronic signature therefore serves as a technical and legal instrument ensuring the identification of the signatory, expression of consent with the document’s content, and preservation of its integrity. The introduction of electronic signatures has enabled the transition from paper to digital platforms while maintaining legal certainty and evidentiary reliability in contractual relations.
In the following sections, this text will elaborate on the types of electronic signatures—simple, advanced, and qualified—as well as their legal significance and application under domestic legislation and the European eIDAS Regulation (EU No. 910/2014).
Electronic Signature: Types, Importance, and Legal Framework
The electronic signature is one of the fundamental institutions of the digital age, providing secure, efficient, and legally valid communication between natural and legal persons. Its application is extensive, covering areas such as the exchange of commercial contracts and public documents, electronic banking, e-commerce, and administrative proceedings. An electronic signature confirms the signatory’s identity, expresses consent to the document’s content, and ensures the document’s integrity after signing.
The European Union adopted Directive 1999/93/EC in 1999 as the first legal framework for the recognition of electronic signatures among Member States, while the United States enacted the Electronic Signatures in Global and National Commerce Act (E-SIGN Act) in 2000, granting electronic signatures the same legal effect as handwritten ones.
In Serbia, the Law on Electronic Signature (2004) was the initial step in this area but saw limited implementation due to insufficient infrastructure and public trust. It was replaced by the Law on Electronic Document, Electronic Identification and Trust Services (2017), harmonized with Regulation (EU) No. 910/2014 – eIDAS, which has, since 2016, directly governed electronic signatures, certificates, seals, and timestamps.
This law clearly defines the types of signatures, the status of trust service providers, and the legal effects of electronic documents, thereby enabling the equal use of electronic evidence in legal transactions.
Conceptual Distinction: Electronic Form, Electronic Document, and Electronic Signature
It is crucial to distinguish between three fundamental concepts:
Electronic form refers to an abstract method of expressing legal content in a digital medium, regardless of the specific file format or software.
Electronic document is a specific digital record created in electronic form that may have legal effect.
Electronic signature is an electronic datum attached to, or logically associated with, an electronic document for the purposes of authenticating the signatory and expressing consent to its content.
A proper distinction between these notions is essential for applying legal rules in a digital context. It clarifies how legal will is expressed (electronic form), how it is embodied (electronic document), and how its authenticity and consent are confirmed (electronic signature). This differentiation is particularly important when assessing the legal validity and evidentiary value of electronically concluded contracts or other legal acts.
In digital legal transactions, the electronic form expresses intent, the electronic document records that intent in a tangible digital manifestation, and the electronic signature serves as proof of that intent—identifying the signatory and ensuring the authenticity and integrity of the document. These three elements thus constitute logically and functionally connected stages of a single legal act within the digital environment.
Types of Electronic Signatures (SES, AES, and QES)
Pursuant to the eIDAS Regulation (EU No. 910/2014) and the Serbian Law on Electronic Document, Electronic Identification and Trust Services, the following types of electronic signatures are distinguished:
Simple Electronic Signature (SES)
The Simple Electronic Signature (SES) encompasses any electronic data used by a signatory to express consent (e.g., a name at the end of an email, a scanned signature inserted into a PDF, a click on “I accept,” or an electronic confirmation of an order). It does not meet the technical or legal criteria for an Advanced or Qualified Electronic Signature, and thus carries limited evidentiary value.
Under the principle of informality established in the Law on Obligations, SES may suffice where no specific form is prescribed by law. However, for legal transactions requiring authentication or a prescribed written form (e.g., real estate or copyright contracts), SES is not sufficient.
Its legal effect depends on the circumstances of the case—such as prior dealings between parties or the existence of technical evidence (IP logs, email headers, timestamps)—that can confirm authenticity.
Advanced Electronic Signature (AES)
The Advanced Electronic Signature (AES) must satisfy several criteria:
It is uniquely linked to the signatory;
It enables reliable identification of the signatory;
It is created using means under the exclusive control of the signatory;
It is linked to the data in such a way that any subsequent alteration can be detected.
AES provides a balance between security, legal validity, and accessibility—it does not require a qualified certificate yet ensures a high degree of reliability. Based on asymmetric cryptography (private and public keys), it guarantees authenticity, integrity, and timestamping of the document.
AES is widely used in B2B contracts, internal corporate documentation, e-commerce, banking, and public administration, though it is not sufficient for transactions requiring the legal effect of a handwritten signature.
Commercial Platforms
Numerous commercial platforms offer AES solutions compliant with the eIDAS Regulation:
DocuSign – supports AES and, in certain EU jurisdictions, QES through partnerships with QTSPs; includes audit trail and multi-factor authentication.
Adobe Acrobat Sign – provides AES and QES with timestamping and integration within the EUTL/AATL trust provider network.
Signicat – integrates with national e-ID schemes (BankID, MitID) and is used in financial and public sectors.
Namirial (Italy) – an accredited QTSP offering AES/QES services in full compliance with eIDAS.
Dropbox Sign – an accessible solution featuring timestamps and IP logs, suitable for small and medium enterprises.
The Advanced Electronic Signature (AES) thus occupies a mid-level position between the simple and qualified signatures, offering an optimal balance between legal certainty and practical efficiency, especially in commercial transactions where a QES is not required.
Qualified Electronic Signature (QES)
The Qualified Electronic Signature (QES) represents the highest level of legal assurance and is the only electronic signature legally equivalent to a handwritten one. It is issued by a Qualified Trust Service Provider (QTSP) using a qualified certificate, and is required when the law mandates a written form or where full legal certainty is essential.
