Electronic timestamp – what is it, how does it work and why is it worth using? 1/2

Electronic time stamps have a wide range of applications wherever it is important to record the moment of creation or submission of a document. Here are the most important areas where this service is used:

• Electronic signatures and digital contracts. When concluding civil law contracts remotely or signing important documents electronically, the exact date and time of the signature are crucial. Providing a signature with a qualified time stamp provides a guarantee and legally reliable proof that the document was signed at a precisely defined time. This is particularly important, for example, in contacts with banks or in tender procedures, where the use of time stamps is often required to secure the date of signing the offer. For example, in public procurement in Poland, participants must submit offers using an e-signature from 2021; however, if the signature certificate expires during the evaluation of offers, only prior time stamping of the offer will allow its positive verification after the certificate expires. The lack of a stamp could result in the invalidation of the signature after the certificate expires, which is why the use of time stamps has become the de facto standard in such situations.

• Electronic invoices (e-invoicing). In the circulation of digital invoices, it is important to confirm the date of issue and ensure the authenticity of the document's origin. In the past, invoices in PDF format were often provided with a qualified electronic signature and a time stamp, which created a coherent whole guaranteeing the integrity and certain date of the document. Currently, the National e-Invoice System (KSeF) is being implemented in Poland - a platform for issuing and receiving structured electronic invoices. Each invoice sent to KSeF receives a digital time stamp assigned by this system. Such a stamp certifies the time of receipt of the invoice in the system and protects it against later manipulation. Thanks to this, both the issuer and the recipient of the invoice have official confirmation of the time of issue of the document, which is important for tax settlements and payment deadlines. Although the introduction of the mandatory KSeF for all entrepreneurs has been postponed until 2026, more and more companies are already voluntarily using e-invoices with a time stamp, appreciating the automatic confirmation of the date of receipt of the invoice.

• Long-term archiving of electronic documents. If digital documents must be stored for many years (e.g. notarial deeds, financial or personnel documentation), the challenge of maintaining their credibility over the long term arises . Over the years, electronic certificates used to sign a document may expire or be revoked, and cryptographic algorithms may lose their strength. Timestamps are a solution for long-term validation : applying a time stamp at the time of signing the document confirms that the signature was made within the certificate's validity period, which will allow for correct verification of the signature even many years later. In addition, periodic renewal of time stamps (e.g. adding another time stamp every few years) allows for extending trust in the document despite potential technological changes. The most rigorous electronic signature profiles, so-called archival forms, even provide for multiple timestamping of the document during its storage. As a result, electronically archived documents retain full integrity and credibility even decades after their creation.

Electronic communication and delivery. The exchange of correspondence by electronic means also uses time stamps. An example is the so-called qualified electronic registered delivery service , regulated by eIDAS – their task is to provide proof of sending and receiving a message along with the time of these events. According to the regulations, evidence of such deliveries must be provided with a qualified time stamp to clearly confirm the time of sending and receiving an electronic shipment. Time stamps also play a role in everyday business communication: if we send important documents by e-mail or the ePUAP platform, it is worth signing them and stamping them with a time so that in the future we can prove exactly when they were sent or submitted. A statutory electronic delivery system is coming into force in Poland, in which official confirmations of submission (UPP) and receipt (UPO) of documents will be automatically provided with time stamps, constituting the digital equivalent of a postmark with a date.