Welcome to UK LLC Guidebook

Welcome to UK LLC Guidebook#

The home of UK Longitudinal Linkage Collaboration’s data documentation and user guide.

Last modified: 19 May 2025

UK LLC is the national Trusted Research Environment (TRE) for data linkage in longitudinal research.
UK LLC brings together de-identified data from Longitudinal Population Studies (LPS) and systematically links these data to study participants’ health, administrative and place-based records in the UK LLC TRE.

UK LLC’s protocol paper, published in the International Journal of Population Data Science, explains how UK LLC works. Currently, researchers can request access to data from 20 LPS, with participants’ records linked to NHS England and place-based datasets where permissions allow. NHS Wales and further place-based datasets will be available in 2025.

UK LLC’s unique attributes include:

  • The dynamic nature of linkages. Linkages to NHS England datasets are refreshed every 6-12 months, and we are able to provide researchers with access to new or updated LPS datasets as they become available, ensuring the temporal alignment of LPS and linked data.

  • The consistent nature of linkages. All linkages, data extracts and post-processing are done in the same way, at the same time, across all LPS. This facilitates cross-study analysis as data are directly comparable.

  • The breadth of data types. UK LLC already contains NHS England and NHS Wales data, plus place-based data. Agreements are in place to flow data from NHS Scotland, from the Department of Work and Pensions (DWP), and from HM Revenue and Customs (HMRC). These data are expected to be available in the TRE in late 2025. Negotiations are ongoing to flow data from the Department for Education (DfE) and Health & Social Care Northern Ireland (HSCNI).

  • The range of linked health records. UK LLC has the maximum number variables permitted by NHS England, across a wide set of linked health records, covering primary, secondary and community-based care.

  • A dynamic library of research products (e.g. syntax, derived variables) being developed by UK LLC researchers is available to all TRE users.

  • The simplicity of the application process. Researchers need to complete just one form to apply for any LPS or linked data. Researchers already working in the UK LLC TRE can apply to access additional data as it becomes available, via UK LLC’s project amendment process.


Please visit:

  • UK LLC Explore (UK LLC’s metadata catalogue) to discover the breadth of data held in the UK LLC TRE.

  • UK LLC Apply (UK LLC’s online application management system) to apply to access data.