The Electoral Commission

The independent body which oversees elections and regulates political finance in the UK

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Accuracy and completeness of electoral registers

Accuracy and completeness of the registers

We measure the quality of the electoral registers to assess how this changes in response to legislative developments, administrative and population changes.

Our most recent research on the electoral registers in Great Britain was published in July 2016 followed by our report on the electoral register in Northern Ireland in September 2016. These reports, along with our previous studies can be found in our electoral registration research report library.

The key findings from our most recent assessment of the electoral registers are outlined below.

Measuring accuracy and completeness

The quality of the registers is measured through two criteria:

  • Accuracy refers to the percentage of register entries that correctly refer to people who are eligible to be registered and are residents at the address the entry refers to.
  • Completeness refers to the percentage of eligible people registered at their current address.

Chart showing how accuracy and completeness are calculated


Our evaluation of the December 2015 electoral registers is based on a house-to-house survey of 6,027 addresses, across 116 local authorities, conducted by trained interviewers with the aim of gathering information from residents which could then be checked against the details held on the registers.

The methodology was built on previous studies conducted by the Commission and has been validated by the findings from a study using census data which are presented in our report Electoral registration in 2011

The December 2015 electoral registers

The research published in 2016 was the final instalment of our research programme designed to measure the impact of the transition to Individual Electronic Registration (IER).

The first study was conducted before the transition to IER started and assessed the registers published in February/March 2014 at the end of the last canvass conducted under the old household system.  The second study was conducted on the December 2015 registers - those published at the end of the transition to IER.

Headline findings

Data collected from our house-to-house survey, checked against the December 2015 registers indicates that overall:

  • the local government registers were 91% accurate and 84% complete
  • the parliamentary registers were 91% accurate and 85% complete

This means that during the transition to IER - 10 June 2014 to 1 December 2015 -  the overall accuracy of the registers increased (by an estimated four percentage points).  Completeness appears to have remained largely stable with a decline of less than 1 percentage point which is not statistically significant

Chart showing completeness and accuracy before and after the introduction of IERNote: * Difference against 2014 estimate not statistically significant.

These estimates are for Great Britain as a whole; the accuracy and completeness of the registers is expected to vary considerably across local authority areas due to the demographics of the local population as well as registration practices.

Decreases in completeness

While the change in completeness from 85% pre IER to 84% post transition is small at the overall level, there are more notable decreases for particular socio-economic groups. Our research confirms the correlation between certain demographics and lower or higher levels of completeness with age and mobility still found to be the variables with the strongest impact: the young and those more likely to move home are less likely to be registered. The specific decreases suggest that there is likely to have been a genuine decline at the headline level.

Population mobility

Our previous research into the registers has found a clear connection between home movement and completeness: as the register is a property-based database, greater mobility is associated with lower levels of completeness while the longer an individual has been resident at their property, the more likely they are to appear on the electoral register. These patterns remain true after the transition to IER:

Chart showing register completeness by length of residenceNote: * Difference against 2014 estimate not statistically significant.

Post IER-transition, the impact of mobility is more pronounced among those who have lived at their address for fewer than two years with completeness falling most among recent movers.


The highest level of completeness is seen for those aged 65+ (96%) and the lowest level is recorded for attainers (16 and 17 year olds, 45%). As the chart below also shows there has been a decline in completeness among those aged under 45. The fall among 18-19 year olds, 25-34 year olds and 35-44 year olds is statistically significant.

The change in the pattern of completeness by age could be a consequence of the introduction of IER. Under the previous household system parents/guardians could register their eligible children living at their address, perhaps explaining the previous higher – although still significantly lower than the overall - levels of completeness among 18 and 19 year olds and their subsequent fall following the introduction of IER.

Chart showing register completeness by ageNote: * Difference against 2014 estimate not statistically significant.

There is a strong correlation between the length of time an individual has lived at their address and the likelihood that they are registered to vote.  Lower levels of completeness among under 35s are firmly connected to mobility with younger age groups significantly more likely to have recently moved home than older age groups. Data from the 2013 – 2014 English Housing Survey shows that 55% of all recent movers are under the age of 34. However, as we have previously argued, mobility alone does not account for lower levels of registration among young people. Lower levels of engagement with politics and voting are also a relevant factor.


There has been a statistically significant uplift in completeness since our last assessment among those who own their property outright, with an increase from 94% to 95%. In contrast, those privately renting have the lowest levels of completeness and the chart shows that there has been a statistically significant decline in levels of registration among this group post-IER transition.

Tenure intersects with age and mobility: both have a significant impact on registration. The private rental sector has the youngest profile of the tenure types: according to the 2014-2015 English housing survey, 48% of private renters are aged between 16 and 34. In contrast 84% of those that own their property outright are over 55. Private renters also tend to live at their address for a shorter amount of time than other tenure groups:

Chart showing register completeness by tenure

The December 2015 registers in context

The December 2015 registers, published at the end of the autumn 2015 canvass and the end of the transition to IER contained 3% fewer entries than the registers used for the May 2015 UK Parliamentary general elections [at the end of the transition any register entry which had not either been successfully matched against DWP data or had personal identifiers provided and verified was removed].

They also predate the changes to the registers made in the run up to the May 2016 elections and the referendum on EU membership held in June 2016. The electorate increased in size by approximately 4-5% during this period. The fluctuation in total number of register entries is represented in diagram below:

Chart showing accuracy and completeness against the number of entries on the electoral register

The full report on the accuracy and completeness of the December 2015 electoral registers in Great Britain along with the report on the electoral register in Northern Ireland and our previous research can be found in our electoral registration research report library.