Modified national versions of the WHO’s International Statistical Classification of Diseases, current version ICD-10 with ICD-11 coming into effect in January 2022, have become the standard in many countries for diagnosis and procedure coding to facilitate the submission of medical billing and reimbursement by health insurers. The WHO ICD-10 exists purely as a coded classification of disease. It has no related classification of procedures and lacks the clinical level of diagnostic specificity necessary for the documentation of individual clinical cases and the associated prescribed therapies and interventions, particularly surgical cases. Historically, the US clinical modification of ICD-9, known as ICD-9-CM, established the trend. Australia adopted ICD-9-CM, later adapted it to Australian clinical specifications, and after the launch of the WHO ICD-10 produced the current Australian modification ICD-10-AM, used under license by many other countries. This paper examines a work in progress, rather than offering an academic critique, to illustrate the evolution of national clinical modification with particular reference to those of the United States, Australia and Thailand. The selection is based on the historical ICD-9-CM connection of the US and Australia, and the fact that Thailand is a more advanced developing nation like Saudi Arabia. The study parameters include the Saudi national healthcare system which has not previously employed a classification clinical coding, despite the wealthy developing healthcare system. Nations using their own modification face the burden of upgrading. Saudi Arabia plans to implement the national Australian modification, rather than creating a Saudi national modification.