Electronic time stamp - what is it, how does it work and why should you use it? 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 is crucial. Affixing the signature qualified time stamp provides a guarantee and legally reliable proof that the document was signed at a precise moment. This is particularly important, for example, when dealing with banks or in tender proceedings, where time stamps are often required to secure the date when a bid was signed. For example, in public procurement in Poland, participants as of 2021 must submit bids using an e-signature; however, if the signature certificate expires during the evaluation of bids, only prior timestamping of the bid will allow it to be successfully verified after the certificate expires. The absence of a timestamp could result in the signature being invalidated after the certificate expires, so the use of timestamps 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, it was common for PDF invoices to be stamped with a qualified electronic signature and a timestamp, creating a coherent whole to guarantee the integrity and date certainty of the document. Currently, Poland is implementing The National e-Invoicing System (KSeF) - 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 marker certifies the moment an invoice is received into the system and protects it from later manipulation. In this way, both the issuer and recipient of the invoice have official confirmation of the document's time of issue, which is important for tax settlements and payment deadlines. Although the introduction of mandatory KSeF for all businesses has been postponed until 2026, more and more companies are already voluntarily using e-invoices with a time stamp, valuing the automatic confirmation of the invoice receipt date.

• Long-term archiving of electronic documents. If digital documents need to be stored for many years (e.g., notarial files, financial or HR records), there is the challenge of maintaining them credibility in the long term. Over the years, the electronic certificates used to sign a document can expire or be invalidated, and cryptographic algorithms can lose their strength. Time stamps are a solution to long-term validation: the use of the tag at the time of signing the document confirms that the signature was made within the validity period of the certificate, which will enable the signature to be correctly verified even many years later. In addition, periodic time stamp renewal (e.g., adding another timestamp every few years) makes it possible to prolong confidence in the document despite potential technological changes. The most stringent electronic signature profiles, the so-called archival forms, even provide for multiple time stamps on a document over the course of its storage. As a result, electronically archived documents retain the full integrity and reliability Even decades after their creation.

Electronic communication and delivery. Electronic correspondence exchanges also use time stamps. An example is the so-called. qualified registered electronic delivery services (Qualified Electronic Registered Delivery Service), regulated by eIDAS - their function is to provide proof of the sending and receiving of messages along with the time of these events. According to the regulations, evidence of such deliveries must be accompanied by a qualified time stamp, to unequivocally confirm the times when an electronic message was sent and received. Timestamps also play a role in everyday business communication: if we send important documents via email or a platform ePUAP, it is a good idea to sign them and stamp them with the date so that you can prove in the future exactly when they were sent or submitted. In Poland, a statutory electronic delivery system is coming into effect, under which official certificates of submission (UPP) and receipt (UPO) of documents will be automatically time-stamped, serving as the digital equivalent of a postmark with a date.