COBOL applications remain embedded in payments, accounts and public administration because decades of business rules, data links and proven transaction processing sit around the code. IBM’s new COBOL Elevate for z/OS, available from 18 September, reflects a market moving toward gradual modernisation rather than wholesale replacement.
COBOL, short for Common Business-Oriented Language, was created for business data processing. It is English-like by design and handles fixed-point decimal arithmetic, useful for financial records where rounding errors are unacceptable. The first version appeared in 1960, but the language is still maintained through standards, including COBOL 2023.
A mainframe is not the same thing as COBOL. A mainframe is a computer platform built to process large volumes of work reliably. It can run several languages. A COBOL program can also run outside a traditional mainframe. The two remain closely associated because many high-volume business systems were built using both.
The code carries accumulated business rules
Replacing a programming language sounds like a technical task. Replacing a decades-old application is an operating-risk project. The software may contain thousands of rules for exceptions, calculations, reporting periods, account states and links to other systems.
Some of those rules will be documented. Others may only be fully expressed in the code and the records it has processed over many years. A new Java or cloud application must reproduce the behavior that customers, employees, regulators and connected systems depend on.
That is why a literal code translation is rarely enough. IBM says a complete modernization program also has to address data architecture, runtime environments, integration and transaction integrity. A payment system that works correctly in most cases is not ready to replace one that has handled rare but consequential cases for decades.
Legacy risk is broader than COBOL
Older systems can become expensive to operate and difficult to change. The US Government Accountability Office identified 11 federal legacy systems most in need of modernization in a 2025 review of 69 systems. Eight used outdated programming languages, four had unsupported hardware or software, and seven had known cybersecurity vulnerabilities.
The findings should not be reduced to a claim that COBOL itself creates a security flaw. Programming language age, unsupported components, access controls and architecture are different issues. They can occur together in an older system, and the real risk depends on how it is maintained and connected.
Skills are also a concern, but the shortage is not limited to COBOL developers. Kyndryl’s 2025 survey of senior business and IT leaders found that 70% reported difficulty finding mainframe-modernization skills. It is a supplier survey, not an independent audit, yet its respondents more often cited AI, cloud and integration skills than legacy languages alone.
Modernisation can keep the core system running
IBM’s COBOL Elevate for z/OS is designed to analyse and optimise existing applications, help teams upgrade compilers and identify code performance issues. IBM says the tool can support some optimisation without source-code changes. Those are product claims, not proof that any particular company’s modernisation problem has been solved.
For many organisations, a more realistic route is to retain the stable core while exposing selected functions through application programming interfaces, known as APIs. Newer services can then use established transaction logic without a one-time rewrite of every component.
The approach creates a hybrid estate, which brings its own operational demands. Interfaces must be tested, data must remain consistent and teams still need people who understand both the existing platform and the new services connected to it.
Our earlier guide to a legacy system explains why age alone is not enough to decide whether software should be retired. A system should be replaced when the cost and risk of keeping it outweigh the cost and risk of a controlled migration. For an application at the center of payments or tax processing, that judgment is often far harder than the language’s age suggests.
