As part of the digital transformation of the Croatian Tax Administration, APIS IT needed to modernize one of the most important foundations of the national tax system: taxpayer registers and supporting public administration records.

The platform covers core registers containing companies and individuals registered as taxpayers in Croatia. These registers serve as a central source of taxpayer data used across Croatian Tax Administration processes and connected public sector systems.

In addition to taxpayer and independent activity records, the project included support for tax card processes, account-related data, codebooks, records from public institutions, local government decisions, annual financial statement data, spatial unit records and reporting.

The challenge was to support a large, long-term modernization of complex legacy processes into a more integrated and automated platform, while maintaining reliability, data consistency and continuity of mission-critical public sector operations.

Kodilion has been engaged on this project since 2023, working across backend development, frontend development, integrations, testing and support.

The solution supports the modernization of central taxpayer records, the Register of Independent Activities, tax card functionality and a broad set of supporting registries and public administration records. The Register of Independent Activities includes business forms such as crafts and other independent activities, while the central taxpayer register represents a key source of data for legal entities and individuals who are taxpayers in Croatia.

The business architecture positions the domain as a foundation for maintaining taxpayer records, managing other registries and auxiliary records, supporting the use of registry data across Tax Administration processes, and enabling data exchange with external institutions.

The use case model covers key areas such as taxpayer records, independent activity records, tax card functionality, data retrieval, taxpayer data review, data exchange, data migration, transition support for legacy systems and reporting.

After the main development phase, the project entered the maintenance phase, covering preventive and corrective maintenance, operational support, incident resolution, monitoring, optimization, upgrades and continued alignment with APIS IT standards.

Technologies: Java 17, Spring, React, SOAP Web Services, REST, DB2 LUW, DB2 z/OS, Maven, Splunk, Apache POI, OpenShift, Kafka, Git

Business Domain: Public Administration, Tax Administration, Digital Transformation, Taxpayer Registers, Independent Activity Records, Tax Card, Registry Management, Government Interoperability

Key Functional Areas: Taxpayer Records, Independent Activity Records, Tax Card, Account Register, HZMO, HANFA, REGOS, Codebooks, eApplications, Local Government Decisions, Annual Financial Statements, Spatial Unit Records, Reporting

Engagement Model: Long-term development, modernization, integration, testing and maintenance support for mission-critical public sector systems