How Welsh Revenue Authority (WRA) statistics meet the Code of Practice for Statistics and the dimensions of value, trustworthiness and quality.

First published:
15 August 2019
Last updated:

Updates to key quality information

Date of the change

Description of the main changes

21 November 2019

Diagram added to these page to explain how we adjust data for operators with different accounting periods.


Introduction of LDT

We introduced these statistics to meet the immediate user requirement for data on Landfill Disposals Tax (LDT), following the WRA being established. 

Statistics published in other UK countries

Statistics for the equivalent taxes in England and Scotland are published by HMRC and Revenue Scotland respectively. Up until April 2018, statistics on landfill disposals in Wales were included in the HMRC bulletin, but not shown as separate values within the England and Wales data.

HM Revenue and Customs - Landfill Tax Bulletin

Revenue Scotland – Scottish Landfill Tax Statistics

In the methods section of the statistical releases, we have set out how we adjust the data to reflect the tax due in the quarter. This allows us to estimate and report LDT due in that quarter.

HMRC report on the tax returns submitted in each month, which depend on the accounting periods of the landfill site operators, and then make some accounting adjustments to reflect quarterly activity. We are unable to publish by month due to the risk of revealing details of individual landfill site operators and we are also keen that the tax reported fully relates to the period against which it is reported. Therefore, please note that data for Wales may not be fully comparable with the data for England published by HMRC.


These statistics have been produced in line with the Code of Practice for Statistics.

As a new producer of official statistics, we are developing our statistical publication processes. We previously published our policy on statistical outputs, including:

  • the professional standards which were adhered to as part of the creation of these statistics;
  • how the content and timing of outputs is independently managed by the WRA Lead Official for Statistics;
  • how we notify users of upcoming outputs;
  • how data is collected, stored and managed; and
  • that staff involved in the production of statistics will undertake continuous professional development in line with the Civil Service competency framework and the Government Statistical Service (GSS) competency framework.


We are still assessing the quality of the data and will continue to do so as more data are received.

We have assessed the interest and potential quality concerns in-line with the Government Statistical Service guidance on the use of administrative data, identifying any potential quality concerns. The table below presents our current assessment.

Data source

Public interest profile

Level of risk of quality concerns

Level of assurance information to be developed

LDT returns



A1 – basic assurance

During the preparation of this release, we have worked closely with WRA operational staff to identify further issues during collection and processing of individual returns. We developed some quality controls around the tax returns which flag up potential areas of concern to our operational staff who can then contact landfill site operators to correct potential issues.

These checks have highlighted that there are some very minor rounding issues within the data that has been supplied to the WRA, mainly due to multiple site submissions and weighbridge rounding. These issues result in internal consistency differences of less than £10 in aggregate, well within the rounding parameters we have used in presenting the results.

A further example of a quality issue we discovered is set out below.


By looking at the internal consistency of the data across all returns, we found some issues where our guidance had been ambiguous and where some water discount weight had been recorded against taxable disposals. We revised the guidance to make it clearer and confirmed that all landfill site operators involved had then followed the new guidance, correcting data as necessary ahead of publication.

Methods used to adjust data for different accounting periods

The majority of landfill site operators have standard accounting periods for reporting to the WRA. These align with the end of our reporting quarters. A small number of landfill site operators use different start and end dates for reporting to the WRA. The attached diagram explains how we account for this issue when producing estimates for the current and previous reporting quarters.


Accounting periods for Landfiill Disposals Tax returns
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Future revisions to data

The data in each release is currently provisional and may be revised in future releases to account for updates to returns, for example following routine mitigation and recovery checks carried out by the WRA.

The methods section in each release covers planned revisions to the data, and the consequent marking of the most recent quarter’s data as provisional. However, the more ad-hoc revisions required following mitigation and recovery checks are less predictable.

For example, there are currently relief claims being assessed and, in these cases, the waste in question has currently been accounted for within the lower rate estimates presented. If the relief is approved the impact may be backdated to cover previous quarters, so that an unplanned revision to the data presented here may arise (although it is likely to be small). Where unplanned revisions are necessary to historic data, we will always make it clear the reasons why in the relevant release.

Coherence with other data

We will soon be able to compare the weight of taxable disposals with some data from waste returns received by Natural Resources Wales. This will allow some further sense checking of the data presented here.