01
What is ELSTER?
ELSTER stands for „Elektronische Steuererklärung“ (electronic tax return). Most people associate it above all with “Mein ELSTER”, the tax authorities' free online portal for filing tax returns electronically. ELSTER, however, refers not only to the portal but to the procedure and the technical infrastructure for submitting tax data electronically.1
Important for the architecture
ERiC stands for ELSTER Rich Client and is a technical component provided by ELSTER for software providers. It is integrated into your own application, or into a dedicated service, and supports the preparation, validation and submission of tax data.
ERiC is not a classic REST API. An application does not simply call a public HTTP endpoint; it embeds a software component provided by ELSTER into its own application. Anyone planning for a classic JSON API mainly budgets for connecting a web service. Anyone using ERiC also has to account for the integration, build, deployment and operation of the technical component.
This very distinction explains why, alongside Mein ELSTER, numerous commercial tax software products exist. Providers such as smartsteuer, wundertax or WISO Steuer build their own user experience and add features to the electronic submission, for example automatic document recognition, pre-filling or additional assistance functions.
02
What does an ELSTER interface do?
An ELSTER interface connects a product's domain data with the structures prescribed by the tax authorities for electronic submission. In practice, a complete integration can be split into four areas of responsibility.
ELSTER integration
Four areas of responsibility
- Data model & payloadInternal domain data is mapped onto the prescribed ELSTER structures and fields.Mapping
- ERiCThe technical component provided by ELSTER is integrated into the application or into a dedicated service.Integration
- Authentication & securityCredentials, certificates and other security-relevant information have to be kept separate, protected and auditable.Credentials
- Communication & responsesTransmission, technical responses and errors have to be processed inside the product and presented in a way that users and support staff can understand.Error handling
This separation also matters for troubleshooting. A mapping error, for example, originates in your own application code, while a problem with the integration or the runtime of the technical component has to be investigated somewhere else. Responses from the submission process form yet another class of errors. If these cases are not distinguished in the logs, troubleshooting and support become harder.
03
How much effort is your own ERiC integration?
The effort depends on the procedure being supported, the existing data model, the target platforms and the requirements for operation and scaling. The submission itself is only one part of the job. The integration becomes demanding above all where your own product meets ELSTER's prescribed structures and technical requirements.
Your own data model does not match the official form structures
A software product's internal data model is usually not identical to the structures of the official tax forms. Between the two sits a translation layer that has to be built, tested and maintained whenever the supported procedures change.
Validate before ERiC validates
Not every input check should happen only immediately before submission. It makes sense to validate at the point of entry, for example mandatory fields, data types, value ranges or field lengths.
That way users get understandable hints such as “Please enter the distance in kilometers” instead of a technical error message only once the return is submitted.
A native component in your own deployment
ERiC is integrated as a technical component into your own application or into a dedicated service. The component provided by ELSTER is designed as a C library. That means ERiC is not a standalone web application but a program library that is linked into your own software.
Integrating a C-based component into a modern deployment chain touches base images, platform compatibility, process boundaries and resource consumption, among other things. Depending on the architecture, timeouts, parallelization and retry logic also have to be considered.
A separate service can encapsulate these runtime requirements and decouple the technical integration from the main application. This makes it possible, for example, to organize the release cycle of the tax logic independently of the rest of the product.
Translating ERiC responses into information end users can understand.
Technical return values have to be translated into understandable information inside the product. A clean integration therefore distinguishes, for example, between errors from your own validation, problems generating the data record, technical errors of the integrated component, and responses from the submission process.
Logging, monitoring and transparency in operation
Responses and technical status information should be logged in such a way that support can trace a case without having to resubmit it unnecessarily. In operation, error classes, frequencies, the versions in use and aborted cases should be monitored, among other things.
04
Developer registration with ELSTER
Anyone who wants to use ERiC as a software provider first has to go through the tax authorities' designated developer and provider process1.
- Registration as a software provider or developer
- Review of the intent to develop software by the responsible IT department of the Bavarian State Tax Office
- Dispatch of the credentials for the developer area
- Download of ERiC via the developer area
- Application for the provider ID (Hersteller-ID) via the designated form portal
- Subscription to the ELSTER newsletter for change notifications
This information reflects the state of research in 2026 and is not binding. What always applies are the current details and requirements in the tax authorities' official developer area.
For project planning, the registration and approval process should be treated as a lead time of its own. Before go-live, the integration should also be checked in a suitable test environment.
05
Operation after go-live
An ELSTER integration does not end with the first successful go-live. Changes to tax procedures and forms, as well as new ERiC versions, can make adjustments to your own software necessary.
Ongoing operation therefore requires a recurring maintenance cycle:
Integration Test Release Monitoring Update
So that changes do not turn into a separate project every time, fixed processes and responsibilities for updates, tests and releases should be established from the outset.
Recommended prerequisites for stable operation:
- Defined responsibilities for versions and updates
- Documented dependencies and reproducible build and deployment processes
- Regular and, wherever possible, automated functional tests
- Consistent monitoring after every new release
06
Build vs. buy
When choosing between building and buying, the main question is where technical and operational responsibility should sit. Should your own team own the ELSTER integration, its updates and its operation, or should part of these tasks be handed to a specialized provider?
Build: your own ERiC integration
With your own ERiC integration, your team handles the technical implementation and ongoing operation itself. That includes in particular mapping, integration of the technical component, tests, updates and deployment.
Buy: external solution
With an external solution, the technical ELSTER integration is provided partly or entirely by a specialized provider. Your product then does not integrate ERiC directly, but the provider's interface.
| Build: your own ERiC integration | Buy: external solution | |
|---|---|---|
| Engineering effort | Higher: mapping, component and tests sit with your own team | Lower: the technical integration is partly outsourced |
| Control | High: architecture and release timing stay in-house | Depends on the interface and the provider |
| Maintenance | In your own engineering team | Partly or mostly with the provider |
| Release responsibility | Your own releases whenever relevant changes occur | Depends on the provider's releases |
| Time to market | Usually slower, including access and integration effort | Usually faster |
| Operational complexity | High: component, monitoring and updates | Lower, part of the responsibility sits with the provider |
| Dependency | Lower, but full responsibility of your own | Greater dependency on the provider, its procedures and its schedules |
Companies should first assess how important tax submission is for their own product. In a tax software product it can be a central part of the offering. In a banking, accounting or fintech application it may be only an embedded feature.
Anyone building it themselves has to plan for the permanent technical and organisational effort. Anyone buying should check carefully which procedures and forms are covered, how updates are delivered, and how outages or changes are handled.
07
Final checklist before you start
Anyone evaluating the implementation of their own ELSTER interface should clarify the following core questions up front:
- Which submission procedures and schedules should the product support?
- Which data already exists in your own product, and which information has to be collected in addition?
- Where does the mapping layer sit, and who maintains it when procedures or forms change?
- Which plausibility and input checks happen inside your own product before data is submitted?
- How are credentials and certificates managed securely?
- How are technical responses translated into statements that users and support can understand?
- Which classes of errors can occur, and how are they monitored?
- Who handles testing, approval and rollout of new versions?
- Who carries the permanent technical responsibility in ongoing operation?
08
Frequently asked questions
What is ERiC?
ERiC stands for ELSTER Rich Client. The tax authorities provide the technical component for software providers together with the corresponding interface specification. Software providers integrate ERiC into their application in order to prepare and validate tax data for electronic submission and hand it over to the ELSTER procedure.
What is the difference between ELSTER and Mein ELSTER?
ELSTER refers to the procedure and the technical infrastructure for submitting tax data electronically to the tax authorities. Mein ELSTER is the tax authorities' online portal through which citizens and companies can submit tax data electronically. Commercial tax software can use the same ELSTER procedure technically, but offers its own user interface and additional functions on top.
Is ERiC a REST API?
No. ERiC is a technical component for integration into software and therefore differs architecturally from a classic REST API, which an application addresses over HTTP via defined endpoints.
Can ELSTER be integrated into a SaaS platform?
Yes. The integration involves more than a single API call, though. Data mapping, integration of the technical component, management of credentials, validation, error handling, deployment and ongoing updates have to be treated as one connected technical task.
How much effort is your own ERiC integration?
The effort depends in particular on the procedure being supported, the existing data model, the target platforms and the requirements for operation and scaling. Besides the technical integration, mapping, tests, error handling and ongoing updates above all have to be taken into account.
When does your own ERiC integration make sense?
Your own ERiC integration can make sense when electronic tax submission is a central part of your product and the team wants to own the technical integration, maintenance and operation itself.
The effort depends in particular on the procedure being supported, the existing data model, the target platforms and the requirements for operation and scaling.
Sources
- [1] ELSTER, information for developers and software providers
- [2] ELSTER, press and figures (as of 31 August 2026)
- [3] Landesamt für Steuern Rheinland-Pfalz, filing a tax return by app with a single click
- [4] ELSTER, software products
Retrieved on 9 September 2026. What is binding for procedures, components and access are the current details published by the tax authorities. Statements about our own architecture are based on the implementation at AnyTax.
Last updated: 9 September 2026
Wie AnyTax das löst
AnyTax stellt Partnerplattformen die Infrastruktur für die deutsche Einkommensteuer bereit. Die Anbindung an ELSTER und die dazugehörige Steuerlogik laufen bei uns im Backend.
Welche Integrationswege es gibt und wie die Aufgaben zwischen Ihrer Plattform und AnyTax verteilt sind, steht auf der Integrationsseite.
