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'Every clinical trial must be registered on a publicly accessible database before recruitment of the first subject"1

It is government policy in the UK to promote registration of clinical studies and open access to research findings affecting health and social care. Without registration (and the ability to track and publish research outcomes), healthcare professionals, researchers, patients and the public would remain unaware as to which research has completed and published and which is still ongoing which could lead to potential duplication of effort (which would not only be a waste of time and resources but unethical to subject participants to research where the evidence is already available).

Which studies should be registered?

Registration of clinical trials in a publicly accessible database is a condition of the favourable ethical opinion. The studies for which registration has now been mandated includes the first four categories on IRAS Project Filter Question 2:

  • Clinical trial of an investigational medicinal product (CTIMP)
  • Clinical investigation or other study of a medical device
  • Combined trial of an investigational medicinal product and an investigational medical device
  • Other clinical trial to study a novel intervention or randomised clinical trial to compare interventions in clinical practice

Trial registration is not expected necessarily at the time of REC application but must be in place within 6 weeks of the first participant having been recruited. Where registration was not in place at the time of favourable opinion (and where registration is a condition of favourable opinion) the Chief Investigator should take the first formal point of communication with the REC to confirm that registration has occurred, supplying the clinical trial register name and registration number. This may be when advising of a substantial amendment or other communication but should be undertaken in the first year annual report to the REC at the latest.

Where registration is not mandated it is encouraged.

Where should you register?

The table below summarises the main registers that may be applicable (and available) for your particular research study.

Other interventional or observational studies 

All health research 

All health research requiring ethics approval and/or NHS permissions (being prepared through IRAS) will be allocated a unique IRAS ID.

The IRAS ID should be referenced as a minimum in final reports and publications where the research has not been registered elsewhere. 

All sponsored (Noclor partner)

Noclor will provide the Chief Investigator a unique sponsor reference for the research study (when request for sponsorship is submitted) this allows Noclor to track all outcomes of sponsored research.

The sponsor reference should be included on the protocol, in the IRAS form where requested and in all correspondence with the sponsor in regards to the study. For CTIMPs, this sponsor reference etc.



The EudraCT number is a reference allocated by the European Medicines Agency (EMEA) for Clinical Trial of Investigation Medicinal Products (CTIMPs). The EudraCT number is required before a submission to the MHRA (for Clinical Trial Authorisation) can be made (the EudraCT number confirmation receipt must be attached to application).

The EU Clinical Trials Register which is available to the public contains information on all CTIMPs being conducted in the European Union (EU), or the European Economic Area (EEA) which started after 1 May 2004.

Controlled Trials

International Standard Randomised Controlled Trial Number Register (ISRCTN)

For registration of randomised controlled trials and other research study designed to assess the efficacy of health interventions in a human population. This includes both observational and interventional studies. 

NIHR portfolio studies

​All NIHR studies which have a UK CRN ID number are able to register for an ISRCTN through the NIHR CRN portfolio database.

For non-commercial studies this registration is free (funded by the DH).

Other interventional or observational studies

Register with

The registry is maintained by the National Library of Medicine (NLM) at the National Institutes of Health (NIH), USA.



What will happen if you don’t register?

Failure to register where registration is mandated (or where there is a false declaration of registration) will be considered to be a serious breach of the favourable ethics opinion and will be managed by the Health Research Authority (HRA) in accordance with the National Research Ethics Service Standard Operating Procedures (SOPs). 

[1] Article 19 World Medical Association Declaration of Helsinki, Ethical Principles for Medical Research Involving Human Subjects (Adopted in 2008)