The World Health Organization (WHO) International Classification of Diseases (ICD) is the global standard which categorises and reports diseases in order to compile health information related to deaths, illness or injury. 

All inpatient episodes and day cases that contain diagnoses must be recorded to the mandated version of ICD-10. The current version is at the 10th revision. 

ICD-10 is published by the WHO and updated in the UK every three years. Previous versions are listed below, along with the financial year they were mandated for use. The implementation date for each version is always 01 April:

  • ICD-10 5th Edition - 2016 onwards
  • ICD-10 4th Edition - 2012
  • ICD-10 reprinted (with updates and corrections) - 2000 - 2004
  • ICD-10 - 1995

Reference Books

ICD-10 must be used in combination with the associated ICD-10 Rules, Conventions, Standards and Guidance which are published in the ICD-10 Reference Book.

This is updated annually and published on Delen early each year to allow users to familiarise themselves with any changes made to the standards that must be used between 01 April and 31 March each financial year.

Current and previous versions of the Reference Books are available in our Resource Library.

NHS Digital Classifications Browser

The NHS Digital Classifications browser provides online access to the OPCS-4 Classification. ICD-10 content will be added in September 2022.

Learn more about the browser by visiting our Classifications Browser and eVersions page.

Training Resources

Broaden your coding knowledge by accessing our eLearning modules, presentations and most popular publications:

  • A Basic Introduction to Clinical Coding
  • Basic Anatomy and Physiology Module
  • Four Step Coding Process
  • SNOMED CT Awareness for Clinical Coders
  • Coding for Non Coders

COVID-19 and ICD-10

Keep up to date with the latest ICD-10 guidance relating to COVID-19.

Download ICD-10 Data Files

ICD-10 data files for NHS and system supplier implementation are available to download from the TRUD website.

ICD-10 eVersion

We provide electronic versions (eVersions) of ICD-10 and OPCS-4. These consist of the eViewer application into which eVersions of the classification books and standards can be improved and viewed.

More information is available on our Classifications Browser and eVersions page.


Will SNOMED CT replace ICD-10 and OPCS-4?


SNOMED CT, ICD and OPCS-4 are nationally required standards that serve different but related and complementary purposes. In simple terms, SNOMED CT enables the detailed recording of information to support the provision of care, whereas ICD and OPCS-4 enable the statistically valid counting of diseases, other health conditions, interventions and procedures to support epidemiology and health care management.

Will clinical coders be needed once SNOMED CT has been implemented across the NHS?


Finished Consultant Episodes (FCEs) are coded by clinical coders, using the classifications products in accordance with national standards. The role of the clinical coder will evolve as electronic patient records (EPRs) become more common and as SNOMED CT and future classifications products (such as ICD-11) are implemented. However, the coding process requires experienced human beings to review the clinical notes, discuss with clinical colleagues and exercise judgement in the application of national standards to ensure that FCEs are coded reliably.

presentation on how SNOMED CT and clinical coding can work together is available in the Resource Library.

Will Clinical Coding Audit and Training be part of the Data Security and Protection Toolkit?


Both Acute and Mental Health Trusts are deemed ‘Large Organisations’ in the Data Security and Protection Toolkit (DSPT).

Clinical coders must refer to Data Security Standard 1 in the DSPT Assertion 1.7 Data Quality (Evidence codes 1.7.2, 1.7.3, 1.7.4) for clinical coding audit assertions and evidence requirements.

Clinical coders must refer to Data Security Standard 3 in the DSPT Assertion 3 Training (Evidence code 3.4.3) for clinical coding training, i.e. Specialist Training, assertions and evidence requirements.

Guidance is now available within our Resource Library on the Data Security Standard 3 Training and Data Security Standard 1 Data Quality for Acute and Mental Health Trusts.

For an Organisation to be Satisfactory they must complete all of the mandatory evidence items in their toolkit. Evidence items 1.7.2, 1.7.3 and 1.7.4 (covering clinical coding audit) and 3.4.3 (covering clinical coding training) are mandatory items.