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Publication, Part of

Hospital Admitted Patient Care Activity 2019-20

National statistics

National Statistics

Data Quality Statement


HES data includes patient level data on hospital admissions, outpatient appointments and A&E attendances for all NHS trusts in England. It covers acute hospitals, mental health trusts and other providers of hospital care. HES includes information about private patients treated in NHS hospitals, patients who were treated in England but who were resident outside England and care delivered by treatment centres (including those in the independent sector) funded by the NHS.

Healthcare providers collect administrative and clinical information locally to support the care of the patient. These data are submitted to the SUS to enable hospitals to be paid for the care they deliver. HES is created from SUS to enable further secondary use of this data.

HES is the data source for a wide range of healthcare analysis used by a variety of people including the NHS, government, regulators, academic researchers, the media and members of the public.

HES is a unique data source, whose strength lies in the richness of detail at patient level going back to 1989 for APC episodes, 2003 for outpatient appointments and 2007 for A&E attendances. HES data includes:

• specific information about the patient, such as age, gender and ethnicity;

• clinical information about diagnoses, operations and consultant specialties;

• administrative information, such as time waited, and dates and methods of admission and discharge; and

• geographical information such as where the patient was treated and the area in which they live.

The principal benefits of HES are in its use to:

• monitor trends and patterns in NHS hospital activity;

• assess effective delivery of care and provide the basis for national indicators of clinical quality;

• support NHS and parliamentary accountability;

• inform patient choice;

• provide information on hospital care within the NHS for the media;

• determine fair access to health care;

• develop, monitor and evaluate government policy;

• reveal health trends over time; and support local service planning.


The HES publications focus on headline information about hospital activity. Each annual publication includes a series of national tables and also provider-level breakdowns for some main areas. Most data included in the published tables are aggregate counts of hospital activity. Where averages are published, e.g. average length of stay for inpatients or caesarean rates for maternity statistics, these data are clearly labelled stating how the data has been calculated.

Accuracy and reliability

The accuracy of HES data is the responsibility of the NHS providers who submit the data to SUS. These data are required to be accurate to enable them to be correctly paid for the activity they undertake. NHS Digital has a well-developed data quality assurance process for the SUS and HES data. It uses an xml schema to ensure some standardisation of the data received. The use of the schema means that the data set has to meet certain validation rules before it can be submitted to SUS. NHS Digital leads on the schema changes and consults the data suppliers about proposed changes.

Each month NHS Digital makes data quality dashboards available to NHS providers to show the completeness and validity of their data submissions to SUS. This helps to highlight any issues present in the provisional data allowing time for corrections to be made before the annual data are submitted.

An external auditor, acting on behalf of the Department of Health and Social Care (DHSC), audits the data submitted to SUS to ensure NHS providers are being correctly paid by PbR for the care they provide.

NHS Digital validates and cleans the HES extract and derives new items. The team discusses data quality issues with the information leads in hospital trusts who are responsible for submitting data. The roles and responsibilities within NHS Digital are clear for the purposes of data quality assurance, i.e. to assess the quality of data received against published standards and report the results.

Data quality information for each year to date HES data set is published alongside the provisional year to date HES data, and also alongside annual publications. These specify known data quality issues each year, e.g. if a trust has a known shortfall of secondary diagnoses. The statisticians can only check the validity and format of the data and not whether it is accurate, as accuracy checking requires a level of audit capacity and capability which NHS Digital does not currently possess. Learn more about HES data quality

NHS Digital also publishes a regular Data Quality Maturity Index for providers across several datasets including HES. The UK Statistics Authority conducted case studies of quality assurance and audit arrangements of administrative data sources. HES was used as a case study and further information can be found in the published report (Annex C, case study 3),

Data Completeness - Admitted Patient Care

The HES APC 2019-20 data set includes records of admitted patient episodes collected from 484 providers in England and a single private provider site in Wales which accepts NHS commissioned work from NHS England.

Table 3 provides a count and percentage of FCE records that have valid data in specific key fields.


Table 3: Count of FCEs with a valid entry in fields






Per cent


Per cent






Age at start of episode





Gender (including Not Stated)





Ethnic Category (inc. Not Stated)





NHS number (including Untraced)





Primary Diagnosis Codes





Main Specialty










Final and Provisional Data Comparison

Collection of HES data is carried out on a monthly basis throughout the financial year, with a final annual refresh (AR) once the year end has passed. Each monthly collection refreshes data back to the start of the financial year.

Providers are no longer offered the opportunity to re-submit data for HES after the submission deadline (top-up files), which was approved by partners on the Data Quality Steering Group (DQSG).  This has enabled us to commit to publishing Annual data earlier than for previous years.  Providers were informed about this decision emphasising the importance to submit data correctly before the inclusion date of 20 May 2019.

Table 4 shows the change from the Month 13 provisional data and the final annual refresh data. 

Table 4: Comparing month 13 and annual refresh data


Month 13

Annual Refresh

Percentage change

Finished consultant episodes (FCEs)




FCEs with a procedure




Ordinary episodes




Day case episodes




Finished admission episodes




Emergency admissions





Table 5 shows the number of FCEs occurring in each month in the last three submission periods of 2019-20, including annual refresh. The number of records per month of activity generally increases as more submissions are made; the completeness of the data increases over time. 

Table 5: Monthly variation in submitted FCE records


Month 12

Month 13

Annual Refresh

Apr 2019




May 2019




Jun 2019




Jul 2019




Aug 2019




Sep 2019




Oct 2019




Nov 2019




Dec 2019




Jan 2020




Feb 2020




Mar 2020





Months 1 to 13 are published here in the 'Provisional Monthly HES for Admitted Patient Care, Outpatient and Accident and Emergency Data - April 2019 to March 2020 - Data completeness' document.  

Data Completeness – Adult Critical Care

Of the 34 critical care fields collected in HES, only 14 are mandatory. A summary of completeness of some key fields is shown in the table below, also available as Table 16 in the accompanying Data Tables file (note that, of those fields shown, only ‘unit function’ is mandatory and the others are optional). The table also shows completeness of three key fields in the associated APC episode records. Completion rates are broadly similar to those for the previous year (see Table 16 in the accompanying Data Tables file).

Over-counting of critical care periods

Most raw critical care records in the data set are associated with only one record of an APC episode, but some are associated with multiple episodes as an APC spell; to avoid multi-counting these critical care records, an algorithm has been applied to link each critical care record to the APC episode record against which it is the ‘best match’. Because of limitations in the algorithm, a small number of raw critical care records are identified as a ‘best match’ with more than one APC episode and the final presented numbers of critical care records slightly over-count the true number of critical care periods.

A more detailed discussion of the algorithm and its impact is presented in the accompanying Technical Guide, and Table 17 in the accompanying data file shows a breakdown of application of the first step of the best match algorithm.

The table below illustrates the impact of applying the best match algorithm against the raw critical care / APC episode records to remove duplicates from the analysis:

Table 6: Number of Critical Care records ending in 2019-20


Annual refresh data

Limited to best matches

Number of Critical Care periods



Number of patients



Number of records



Note that the count of number of patients and distinct critical care periods before and after the application of the best match algorithm is different prior to 2013-14. The reason for this is that a change in the data structure of HES has taken place which means that records with no support day data recorded are excluded from the best match setting process.

Under-reporting at financial year boundaries

Much data associated with HES APC records, including associated critical care records, is not reliably complete until the episode or critical care period is finished. Critical care periods associated with hospital APC episodes which are still ongoing at the end of the period of coverage (i.e. at the end of March 2020) will not be reported into the system until the following financial year, when they have finished, and are therefore not included for analysis. As a result, reported figures are lower than the true figures for the full financial year, and, in particular, analysis by month (including the Table 1 in the ACC tables) will present artificially depressed figures for March.

Figures for March each year are artificially depressed as any critical care period associated with a hospital APC episode which is still on-going at the end of March will not be reported into the system until the following financial year, when it has finished.

Default critical care start and end times

The critical care database includes fields recording the time of day at which the critical care period started and ended, albeit that the start time field has been completed in only 263,975 of the 286,224 critical care records used for analysis.

Although the times submitted are not specified to be rounded, it is clear from analysis of the data that there are rounding peaks at each multiple of 5 minutes past the hour, larger peaks at multiples of 10 minutes (and, for end times, at 59 minutes past), still larger peaks at multiples of 15 minutes, a yet larger peak at 30 minutes past the hour and the largest peak at 0 minutes past the hour; this suggests that in many cases the times are being rounded to 5, 10, 15, 30 or 60 minute boundaries.

Timeliness and Punctuality

HES data are published as early as possible. The production of the underlying annual HES data sets takes several months after the reference period. The final submission deadline for NHS providers to send annual data to SUS is normally at the end of May, almost two months after that year has finished. It then takes approximately two months to produce the HES APC data set and a further two months to complete publication production and data investigation.

In addition to annual data NHS Digital also publish provisional monthly HES data approximately two months after the reference period.

The final annual data includes additional data cleaning, validation and processing than the provisional monthly data.

NHS England – Critical Care Beds

Since August 2010, first the Department of Health (DH) and now NHS England has conducted censuses of the numbers of available and occupied critical care beds on the last Thursday of each month; prior to August 2010, similar censuses were conducted by DH twice a year.  These reports can be found at:

Although the number of critical care beds on a given day is not directly comparable with the number of critical care periods which covered that day, a comparison between the two reveals that there are substantial differences between reporting by NHS providers to NHS England’s censuses and to the Critical Care Minimum Dataset and thus in the HES data warehouse from which this publication’s data is drawn.

In particular, there were a number of hospital providers which submitted critical care bed data to NHS England’s census but not to HES; figures reported in this publication are therefore thought to represent an undercount of the true critical care situation; conversely there were a far smaller number of providers for which there is a critical care data in HES but which did not submit any data to NHS England’s census. 

Although differences in the data collections and definitions means numbers of beds / records are not directly comparable, a full comparison between NHS England’s census numbers and HES critical care record numbers, broken down by provider organisation, is included in Table 18 of the accompanying Data Tables file.

UK Comparisons

Separate collections of hospital statistics are undertaken by Northern Ireland, Scotland and Wales. There are a number of important differences between the countries in the way that data measures are collected and classified, and because of differences between countries in the organisation of health and social services. For these reasons, any comparisons made between HES and other UK data should be treated with caution.

ONS used to produce UK Health Statistics which contained key figures about the use of health and social services, including hospital admitted patient activity and waiting times across the UK.

Other UK Data

Hospital data for the other administrations can be found at: 

NHS England also publish hospital activity data


Wider International Comparisons

HES and similar statistics from the devolved administrations are used to contribute to World Health Organisation (WHO), Organisation for Economic Co-operation and Development (OECD) and Eurostat compendiums on health statistics.

Improvements over time

HES data are available from 1989-90 onwards. Changes to the figures over time need to be interpreted in the context of improvements in data quality and coverage (particularly in earlier years), improvements in coverage of independent sector activity (particularly from 2006-07) and changes in NHS practice. 

Payment by Results (PbR) is a system whereby hospitals are paid for the number of patient treatments, known as activity, they perform and the complexity of these treatments. It was introduced in a phased way from 2003-04 onwards. In order to get paid correctly, hospitals need to record the activity they perform and the clinical codes that outline the patients’ conditions and treatment.

The introduction of Payment by Results (PbR), increased private sector involvement in the delivery of secondary care and brought about some changes in clinical practice (including some procedures occurring as outpatient appointments instead of hospital admissions). It is likely that these changes will have affected trends.

This has provided a major financial incentive for hospitals to ensure all of the activity they perform and the clinical coding is fully recorded. This improved recording of information captured by HES could be one of the factors leading to the reported activity increases.

In order to manage patients’ waiting times there has been the need for additional elective operations to be performed as well as a requirement for more capacity in NHS funded care to perform this activity. In the middle of the last decade, additional capacity was brought in from the private sector via treatment centres, with the NHS funding some patients to be treated there for routine operations.

Improvements in technology and the need to increase efficiency to allow more patients to be treated have led to a reduction in the length of time patients need to stay in hospital for certain planned operations. In particular, many of those operations that would have involved an overnight stay at the start of the period are now routinely performed as day cases. In addition, many operations where a patient would have been admitted to hospital at the start of the period are now routinely performed in outpatients. This has led to increases in day case rates and outpatient attendances over the period.

The recent period has also seen a rise in the number of emergency admissions. One factor contributing to this is likely to be the increased demand on health services from an ageing population. Alongside this there has been the introduction of observation or medical assessment units at many hospitals to which patients arriving in A&E departments are admitted, often for around a day, to enable observation and tests to be performed on them.

Care should be taken when interpreting these changes, as improvements in coverage in HES will contribute alongside growth from increased activity.

Last edited: 18 November 2020 2:17 pm