The ADDISON interface in Opti.Tax: what you need to know
What is the ADDISON interface in Opti.Tax?
The ADDISON interface connects Wolters Kluwer’s ADDISON software system, which is used in many law firms, with the Opti.Tax compliance documentation and financial reporting platform. This enables access in Opti.Tax.
What benefits does the ADDISON interface in Opti.Tax offer me?
Data already recorded in ADDISON – such as client and practice master data, financial accounting and management accounting data, and more – does not need to be re-entered for projects in Opti.Tax. This prevents data entry errors and saves a great deal of time, which the practice’s staff can then use for other tasks.
Who stands to benefit most from the ADDISON interface in Opti.Tax?
First and foremost, everyone who works with ADDISON stands to benefit. This includes, in particular, law firms, which can save a great deal of time and work more efficiently thanks to the interface. Furthermore, clients also benefit, as they are charged for fewer services and fewer errors occur.
The interface is integrated into Opti.Tax and is working.
The ADDISON interface has proved its worth over many years of intensive use.
Data transfer always takes place in a controlled and traceable manner.
Working with the ADDISON interface in Opti.Tax

How the ADDISON interface reduces the workload
The right information for the right project
The import should not be viewed as an uncontrolled, wholesale import. Depending on the project, the required data is selected, imported into Opti.Tax and then technically checked, supplemented and documented there. This ensures that the process remains clear and traceable.
Added value for law firms with a large client base
The greatest benefits are realised particularly in the case of recurring tasks and large client portfolios. A standardised retrieval process reduces the number of individual steps per project and ensures more consistent data sets. Staff can focus more on auditing, consultancy and specialist matters.
Specialised compliance processes based on existing data
Opti.Tax is not intended to replace ADDISON, but rather to act as a specialist supplementary system. ADDISON provides the existing database; Opti.Tax guides users through the relevant taxonomy, structures inputs, supports validation, documents processing steps and generates the required results.
Before-and-after comparison
FAQ – Frequently Asked Questions
With the ADDISON interface in Opti.Tax, you can access your system data directly from within the software. We have answered the questions we have received from interested professionals on your behalf.
If you have any further questions, please do not hesitate to get in touch. We look forward to hearing from you.

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About hsp – Software innovation made in Germany
Since 1991, hsp Handels-Software-Partner GmbH has been developing professional software solutions for tax consultancy and audit firms, as well as for businesses.
Our taxonomy software Opti.Tax has established itself amongst discerning professionals in the DACH region as the reliable, high-performance and long-term solution for electronic invoicing. The digital tools for legally required, GoBD-compliant documentation are particularly popular.
Practical relevance, up-to-date content and genuine service
Our software modules are developed in close collaboration with experienced partner firms such as Energiesozietät GmbH for internal control systems (IKS), ADKL Abels Decker Kuhfuß & Partner mbB for transfer pricing, and Schröder & Partner for the digital pension file. In this way, we ensure that the features in Opti.Tax are tailored to the real-world challenges of day-to-day professional practice.
Regular updates ensure that changes to legislation and new requirements are incorporated into the software in a timely manner. In addition, we support you with a comprehensive range of service and support offerings, e-learning courses, access to the hsp Community, our weekly live broadcast „hsp live at 11“ and much more.







