What is a core banking system?

A core banking system is the software that keeps a bank's official records of accounts, balances, deposits, loans and postings. It applies product rules, calculates interest and fees, and feeds the general ledger. Mobile banking, branches, cards and payment services connect to the core but remain separate channels and applications.

A transaction reaches the core through an interface, passes authorization and product checks, and becomes a debit and a credit. The resulting balance is the record other systems rely on. Typical modules and features cover customer and account management, deposits, loans, payments, interest, fees and accounting. A lean-core architecture keeps only posting and product logic in the center and moves other functions to connected services.

The core gives every channel one source for balances and account status. Integration matters because fraud systems, regulatory reporting, card processors and payment rails need timely postings. German savings banks mainly use OSPlus and cooperative banks use agree21. Private banks often operate their own platform or a commercial product. The Germany page compares these structures and known migrations.

A core banking system migration strategy must move accounts and posting histories while daily business continues. Reconciliation must prove that opening balances, accrued interest and every migrated transaction agree. A failed cutover can block payments and customer service. Banks therefore migrate products in waves and keep a tested rollback or containment plan for each stage, including when a cloud core banking platform is involved.

DORA treats a core platform and its hosting as ICT services supporting critical or important functions. The bank remains responsible, records provider contracts, tests resilience and prepares an exit. The DORA text applies across the EU. Accounting, data protection, outsourcing and prudential rules continue alongside it.

BaFin and the ECB supervise German banks, the FMA supervises Austrian institutions and FINMA supervises Swiss banks. Outsourcing does not transfer management responsibility in any of these markets. Frankfurt is home to Finanz Informatik and to supervisors and payment infrastructure that many German cores connect with. A core system is bank-internal software, not a replacement for T2, TIPS or a securities depository.