The Once-Only Principle
Complicated applications, endless forms and time-consuming visits to public authorities make administrative procedures very tedious. Digital services are also not always designed to be user-friendly. This costs applicants time, money and patience. For example, documents have often to be submitted multiple times, even though public authorities already hold much of the information.
The Once-Only Principle aims to change this: In future, citizens and businesses should only have to provide certain details, such their as date of birth and address, once. Public authorities can then reuse this data and supporting documentation, provided this is legally permissible. This makes the Once-Only Principle a key building block of a modern digital public administration. It promises:
This requires registers, specialist IT systems and portals to be securely interconnected, to use common standards, and ensure transparency when data is retrieved.
Parental allowance (Elterngeld) provides an example of how much administrative work could be reduced. Currently, applying involves considerable effort because various supporting documents, such as birth certificate and proof of income, have to be obtained, copied and submitted. According to the Once-Only Principle, public authorities could receive many of these documents directly in future. Citizens would then only need to initiate the application process.
Definition: What is the Once-Only Principle?
The Once-Only Principle is a principle and objective of digital public administration under which citizens and businesses only need to submit data and supporting documents to the government once. Instead of submitting paper documents such as birth certificates, registration certificates (when registering a place of residence) or business registrations with every application, public authorities retrieve this information directly from existing registers, with the consent of those involved and with a high level of transparency in data processing. This saves time, reduces bureaucracy and prevents citizens entering the same information repeatedly. Two initiatives provide the technical and legal foundation: modernisation of registers and the National Once-Only Technical System (NOOTS).
The modernisation of registers enables the practical implementation of the Once-Only Principle. It creates the basis for registers, specialist administrative systems and digital public services to be interconnected and work together seamlessly. This enables secure and traceable data exchange.
From a technical perspective, this data transfer is already possible. With the National Once-Only Technical System (NOOTS), an IT system is in place that manages the legally compliant retrieval of electronic evidence from registers.
In January 2026, NOOTS began operating in a real-world testing environment at a data centre certified by the Federal Office for Information Security (BSI): Initial retrievals of supporting data using real information are now being carried out successfully in two use cases. These involve retrieving data from the Federal Motor Transport Authority’s (KBA) vehicle register, used to apply for a residents’ parking permit, and retrieving information from the commercial register when registering a business.
The next milestone is scheduled for the end of September 2026. At that point, the central NOOTS intermediary service is due to become operational. It checks whether requests to retrieve supporting documents are authorised. The system will be ready for nationwide technical rollout from autumn 2026.
The diagram illustrates how data should legally be exchanged once an applicant has entered their tax identification number and other personal information at a single point (a public authority): The data is forwarded through interfaces connected to other public authorities.
In line with the Once-Only Principle, data only needs to be entered once. The information is then exchanged between the relevant public authorities in a regulated and traceable manner for further processing.
The legal mandate behind the Once-Only Principle: the Online Access Act (OZG)
The Online Access Act requires the federal, state and local governments to offer their public services digitally for citizens and businesses. Instead of having to visit public authorities in person, services such as re-registering a place of residence, BAföG applications or business registrations will be handled easily online through central portals.
Under the “Once-Only Principle”, supporting documents should in future be exchanged directly between public authorities, eliminating the need for multiple data entries. A secure user account (BundID) provides a universal means of verifying identity and communicating with public authorities. The OZG therefore provides the legal and organisational foundation for the comprehensive modernisation of Germany’s public administration.
EU initiatives: Single Digital Gateway Regulation (SDG Regulation)
The EU has launched several initiatives to create uniform systems with standardised access, such as the eIDAS Regulation. The Single Digital Gateway Regulation (SDG Regulation) is highly relevant to the Once-Only Principle. Adopted in 2018, this EU regulation aims to establish a single digital portal for public services across the EU. At the same time, the SDG Regulation is driving the harmonisation of administrative procedures, for example by providing multilingual information about procedures and clear details about the data collected.
The statutory deadline for implementing the 21 groups of cross-border procedures expired at the end of 2023. While the European Once-Only Technical System (EU-OOTS) is now in operation, national data exchange is being implemented in parallel through Germany’s National Once-Only Technical System (NOOTS). In future, NOOTS is to be connected to EU-OOTS via an intermediary interface (intermediary platform).
How register modernisation and NOOTS enable the Once-Only Principle
Registers are the data foundation of public administration. They contain information needed for many public services, such as residents’ registration data, company information, and supporting documents held in specialist registers. So far, however, this data has not been stored centrally. Instead, it is often distributed across different systems, structured differently, or only accessible within individual specialist administration systems. This has led to isolated solutions that shape day-to-day work. Although the information is available for certain specialist procedures, it cannot readily be used securely and in a standardised way for other public services.
This is exactly where modernisation of registers comes in. It is intended to make registers seamless. Rather than requesting the same supporting documents for each administrative procedure, public authorities can retrieve them from registers in compliance with legal requirements. The Register Modernisation Act provides the legal basis for this. It enables data exchange between 51 government registers and introduces the tax identification number as a cross-register identifier.
The technical infrastructure for this is provided by NOOTS. It enables public authorities to retrieve electronic supporting documents from registers in a legally complaint way and establishes:
- standards
- security requirements
- organisational and legal rules
The associated law, the NOOTS State Treaty, entered into force on 1 February 2026. It governs the establishment, operation, further development and use of the system, initially making its use mandatory for OZG services. Funding for 2025/26 is provided through the budget of the Federal IT Cooperation (FITKO). From 2027, the costs will be shared between FITKO (53.4%) and the federal government (46.6%).Responsibilities are clearly allocated: the IT Planning Council makes fundamental policy decisions, FITKO takes the lead overall, and the Federal Office of Administration (BVA) is responsible for technical implementation and operation.
NOOTS connects requesting public bodies, registers and administrative applications, standardising the secure and traceable exchange of supporting documents. This transforms distributed register data into a shared, accessible infrastructure, laying the foundation for the Once-Only Principle.
The Register Modernisation Act (RegMoG) and the Once-Only Principle are essential tools to ensure that the OZG works in practice.
Why interoperability and data protection are essential
Simply connecting registers and administrative applications is not enough to make the Once-Only Principle to work. The systems involved must also be able to understand and process data consistently. Interoperability is therefore an essential requirement: only when public authorities use common standards, interfaces and data models can information be exchanged securely, accurately and without interruptions caused by switching between digital and paper-based processes across registers, specialist administrative systems and digital public services.
This is particularly important in Germany’s federal administrative system, where federal, state and local governments use different systems, have different responsibilities and follow different processes. To make the Once-Only Principle effective beyond individual administrative processes, the following are needed:
At the same time, data exchange must remain transparent and trustworthy. The Data Protection Dashboard (Datenschutzcockpit) plays an important role here. This application allows citizens and businesses to see which public authority has accessed which data and for what purpose. In addition to data protection requirements, high IT security standards are needed to ensure that sensitive information remains reliably protected.
The Once-Only Principle in the Deutschland-Stack
The Deutschland-Stack aims to establish a unified digital infrastructure for public administration in Germany. It includes the technological foundation, strategic and organisational frameworks, and solutions for public authorities. The Deutschland-Stack is particularly relevant to the Once-Only Principle:
- Digital identities enable individuals and organisations to be identified clearly and reliably.
- The modernisation of registers ensures that existing administrative data can be used seamlessly across different systems.
- NOOTS provides the technical foundations for connecting online services, registers and administrative applications, enabling public authorities to retrieve supporting documents securely and in a standardised way across multiple authorities.
Following decisions by the IT Planning Council on 18 March and 17 June 2026, NOOTS is becoming an integral part of the core services within the Deutschland-Stack ecosystem. Germany’s federal states have committed to connecting to three of the five core services nationwide: eID/EUDI Wallet, NOOTS and FIT-Connect. The federal government, with support from FITKO, is providing most of the funding for the central components. The obligation to connect to and use the system is established by the NOOTS State Treaty. NOOTS is also intended to be compatible with European once-only systems, so that secure data exchange will eventually extend beyond national public services.
The Once-Only Principle is therefore becoming a core element of the Deutschland-Stack: while the stack provides the architectural framework and reusable core components, register modernisation and NOOTS enable legally compliant data exchange.
Benefits and challenges of the Once-Only Principle
The Once-Only Principle can significantly reduce the administrative burden on citizens, businesses and public authorities.
However, these benefits also come with challenges:
Restructuring existing processes and responsibilities to ensure seamless cooperation between public authorities involves considerable organisational effort. Coordination between federal, state and local governments also remains a key task. It is essential that they develop the necessary technical and organisational capabilities.
The Once-Only Principle: the role of the Bundesdruckerei Group
As implementation and technology partners for public administration, the companies within the Bundesdruckerei Group draw on their experience in providing secure register and portal solutions. Practical examples include the Bundesportal as a central access point to public services, and the organ donor register as a digital register solution.
Both demonstrate the components essential to the Once-Only Principle: registers, portals and secure procedures for handling supporting documents must work together reliably so that administrative data can be used in a legally compliant, user-friendly and traceable way.
FAQ: Frequently asked questions about the Once-Only Principle
The Once-Only Principle aims to simplify the exchange of data between citizens, businesses and public authorities. It is designed to ensure that information provided once does not have to be submitted again and can instead be obtained by the relevant public authorities. Data and supporting documents already held in individual registers can then be retrieved quickly and directly. Ideally, applicants would only need to report changes to their information. This makes a significant contribution to reducing bureaucracy and easing the burden on citizens, businesses and public authorities.
The National Once-Only Technical System (NOOTS) ensures that public authorities do not have to request electronic evidence again, but are authorised to retrieve it from connected registers. It connects the administrative systems involved and creates a common framework for secure and traceable data exchange.
Interoperability is an essential technical and organisational requirement for the Once-Only Principle. It enables IT systems used by different public authorities to exchange and process data consistently. Common interfaces, data formats, and standards ensure that information is understood consistently. This allows the Once-Only Principle to work beyond individual authorities and across federal, state and local governments.
The Data Protection Dashboard provides an insight into how administrative data is used. It shows citizens which public authorities have retrieved which data. This makes data retrieval transparent and traceable for those concerned, an essential requirement for building trust in the Once-Only Principle.
