GDP first quarterly estimate, UK

11. Data sources and quality

Reaching the GDP balance

Quarterly GDP is a balanced measure of three approaches. The GDP monthly estimate focuses on gross value added (GVA) and output as a proxy for GDP. This results in data differences, in both levels and growth terms, between our quarterly bulletins (average GDP) and our GDP monthly estimate bulletins (output approach to GDP). Quarterly GDP is the lead measure of GDP because of its higher data content and inclusion of variables that enable the conversion from a GVA concept to a GDP basis.

Information on the methods we use is in our Balancing the output, income and expenditure approaches to measuring GDP report.

Alignment adjustments, found in Table M of our GDP data tables, have a target limit of plus or minus £3,000 million on any quarter. However, in periods where the data sources are particularly difficult to balance, larger alignment adjustments are sometimes needed. This is explained in more detail in our Recent challenges of balancing the three approaches of GDP article.

Our standard practice is to prefer that the alignment adjustment be out of tolerance rather than over-adjust individual GDP components to achieve a balance. This is most likely to occur in the latest quarter, where the constraints are larger, and where we must align to the output estimate for the change in GDP, and where the data content is at its lowest.

To achieve a balanced GDP dataset through alignment, we apply balancing adjustments to the components of GDP where data content is particularly weak in each quarter because of a higher level of forecast content. Table 7 shows the balancing adjustments applied to the GDP quarterly dataset.

Net trade

Since the UK left the EU on 31 January 2020, arrangements for how the UK trades with the EU changed. HM Revenue and Customs (HMRC) implemented some data collection changes following Brexit, which affected statistics on UK trade in goods with the EU.

We have made adjustments to our estimates of goods imports from the EU in 2021 and 2022 to account for these changes. However, a structural break remains in the full time series for goods imports from, and exports to, the EU from January 2021, therefore we advise caution when interpreting and drawing conclusions from these statistics. More detail is provided in our Impact of trade in goods data collection changes on UK trade statistics: summary of adjustments and the structural break from 2021 article.

International Trade in Services estimates

From September 2025 until early 2027, International Trade in Services (ITIS) data (which account for approximately 50% of total Trade in Services) will be processed once each quarterly period. During this period, the data will be based on a robust survey response rate of between approximately 60% and 70%. This will enable more focus on improving processing systems and ensuring methods and quality in the future.

ITIS-based data in Trade in Services estimates at first quarterly estimate will be forecast until early 2027.

The International Passenger Survey (IPS), which is the source of travel services estimates (accounting for approximately 8% of total trade), is being transformed as part of our Improving our travel and tourism statistics project, and travel services estimates have been forecast since Quarter 3 (July to Sept) 2024. Estimates will be forecast during the period of the travel and tourism transformation.

Our Financial Services Survey (FSS) is undergoing transformation to improve the quality of our financial sector statistics. During the period of transformation, starting from Quarter 1 (Jan to Mar) 2024, financial services trade statistics in this bulletin are based on forecasts.

The three approaches to measuring GDP

There are three approaches to measuring gross domestic product (GDP):

• the output approach

• the expenditure approach

• the income approach

The data and data quality are different for each approach, and this dictates the approach taken in balancing quarterly data. There are more data available on output in the UK in the short term, than in the other two approaches. To get the best estimate of GDP, our published figure, estimates from all three approaches are balanced to produce an average, except in the latest two quarters where the output data take the lead, because of the larger data content.

The three approaches to measuring GDP allow us to confront our data sources within the national accounts framework. Figure 3 in our previous GDP bulletin showed that there are differences in the three approaches at this stage in the production cycle for 2025, with real growth estimated in a range of 1.1% to 1.4%. There will be uncertainty at the component level at this stage in the production cycle for 2025 onwards until these data have been confronted through the supply and use tables framework (SUTs). This uncertainty may be for various reasons and is discussed further later in this section.

Output approach

In the output approach, we do not currently have final estimates for intermediate consumption (the value of goods and services purchased to be used up in the production of goods and services). This is outlined in our Blue Book 2025: advanced aggregate estimates article. Initially, we use turnover and output as a proxy for changes in gross value added. We assume that the intermediate consumption ratio by industry, calculated in 2024, holds constant into 2025 onwards. More information on this is provided in Section 11: Data sources and quality of our GDP first quarterly estimate, UK: April to June 2024 bulletin.

Expenditure approach

In the expenditure approach, we currently have lower response rates for areas, such as the Living Costs and Food Survey, which is one of many data sources that inform our estimates of household consumption. We therefore rely on additional indicators, such as our Monthly Business Survey, to quality adjust some of our estimates in the short term.

Income approach

In the income approach, we do not have up-to-date quarterly information on the gross trading profits of businesses. These data are collected from HM Revenue and Customs (HMRC) and are available with a lag of approximately two years.

We rely on contextual data from other sources to inform these quarterly estimates, as outlined in our Profitability of UK companies quality and methodology information (QMI). There is currently more uncertainty around the compensation of employees figures in this release because of lower response rates in our Labour Force Survey (LFS), as described in our LFS: planned improvements and its reintroduction methodology. We have used additional information from our Earnings and employment Pay As You Earn Real Time Information, UK bulletin to help inform the estimates.

Strengths and limitations

The UK National Accounts are drawn together using data from many different sources. This ensures that they are comprehensive and provide different perspectives on the economy, for example, sales by retailers and purchases by households. Further information on measuring GDP can be found in our Guide to the UK National Accounts. More quality and methodology information is available in our GDP quality and methodology information (QMI).

Seasonal adjustment

The headline estimates of quarterly GDP are seasonally adjusted. Seasonal adjustment is the process of removing the variations associated with the time of year, or the arrangement of the calendar, from a data time series.

GDP estimates, as for many data time series, are difficult to analyse using raw data because seasonal effects dominate short-term movements. Identifying and removing the seasonal component leaves the trend and irregular components.

We use the X-13-ARIMA-SEATS approach to seasonal adjustment. Seasonal adjustment parameters are monitored closely and regularly reviewed. For more information, please see our seasonal adjustment methodology page.

In our quarterly GDP estimates, seasonal adjustment is applied at a low level, and the seasonally adjusted series are aggregated to create estimates by sector and total output. As part of our quality assurance approach, residual seasonality checks are regularly completed by our time series analysis team on both the directly seasonally adjusted series, and the indirectly derived aggregate time series.

There are conceptual differences between indirect and direct seasonal adjustment. Indirect seasonal adjustment is the aggregation of the directly seasonally adjusted component series, typically chosen at an optimal level and depending on user needs. For the National Accounts, GDP aggregates are created with indirect seasonal adjustment. Because of processing, including benchmarking and chain-linking, direct seasonal adjustment of the non-seasonally adjusted GDP aggregate will not give the same results as the indirect seasonally adjusted output

Based on our combined assessment from the suite of statistical tests, there is no statistically significant residual seasonality in our aggregate outputs from Quarter 1 1955 to Quarter 3 2026, although we continue to monitor this closely.

This topic is explored further in our recent How the ONS assesses statistical outputs for residual seasonality article, updated on 12 May 2026.

More details can also be found in the Office for Statistics Regulations’s (OSR’s) Compliance review of Treatment of Seasonality in Quarterly GDP statistics and our response to this review.

Important quality information

There are common pitfalls in interpreting data series:

• expectations of accuracy and reliability in early estimates are often too high

• revisions are an inevitable consequence of the trade-off between timeliness and accuracy

• early estimates are often based on incomplete data

Very few statistical revisions arise because of “errors” in the popular sense of the word. All estimates, by definition, are subject to statistical “error”.

Many different approaches can be used to summarise revisions. The section on Accuracy and reliability in our GDP QMI analyses the mean average revision and the mean absolute revision for GDP estimates over data publication iterations. For more information, please refer to our GDP revisions in Blue Book: 2026 article, published on 30 October 2026.

Accredited official statistics

These accredited official statistics were independently reviewed by the Office for Statistics Regulation in October 2016. They comply with the standards of trustworthiness, quality, and value in the Code of Practice for Statistics and should be labelled “accredited official statistics”.

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