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8. Data sources and quality

Data sources

Balance of payments statistics are compiled from a variety of sources, and produced using the national accounts sector and financial accounts (SFA) framework. Some of the main sources used include:

• overseas trade statistics (HM Revenue and Customs (HMRC))

• International Trade in Services Survey (ITIS) from the Office for National Statistics (ONS)

• International Passenger Survey (ONS); this was suspended between March 2020 and January 2021 because of the coronavirus (COVID-19) pandemic, and is currently undergoing transformation

• Foreign Direct Investment Survey (ONS and Bank of England (BoE))

• various financial inquiries (ONS and BoE)

• Ownership of UK Quoted Shares Survey (ONS)

Trade is measured through both exports and imports of goods and services. Data are supplied by over 30 sources, including several administrative sources, with HMRC being the largest for trade in goods. The ITIS, conducted by the ONS, is the largest single data source for trade in services.

The main source of information for UK foreign direct investment (FDI) statistics is our FDI Survey. Separate surveys are used to collect data on inward and outward FDI. This is combined with data from the BoE on the banking sector.

The statistics in this bulletin are compiled using the asset and liability measurement principle, which uses residency as the main distinction between outward and inward investments.

Changes affecting UK trade statistics

HMRC error affecting mineral fuels and oils

In this publication and our GDP quarterly national accounts, UK: July to September 2025 bulletin, we have corrected HMRC Overseas Trade (OTS) data, following the identification of an error. This correction is for exports of mineral fuels and oils and affects data back to March 2024. This release revises data back to Quarter 1 (Jan to Mar) 2024. Please see our UK trade: October 2025 bulletin for further information, including indicative impacts. In line with our National Accounts Revisions policy, we will use the corrected HMRC data in our UK trade: November 2025 release, scheduled for 15 January 2026.

Precious metals methods improvement

As previously communicated, when implementing improvements to recording trade in precious metals as part of our Methods improvements for Blue Book and Pink Book 2025, we removed the double counting of some precious metals bars and included previously under-recorded, non-monetary gold that is not in bar form. 

These improvements, however, were not fully applied to a small number of countries in 2024 and 2025 because of a processing error. For full details including indicative impacts previously published, please see our Balance of payments, UK: April to June 2025 bulletin and UK trade: October 2025 bulletin.  

We have now corrected the processing error and, in this release, we fully implement this improvement. Estimates of trade in goods for Quarter 1 2024 to Quarter 2 (Apr to June) 2025 were updated in our UK trade: August 2025 bulletin and GDP first quarterly estimate, UK: July to September 2025 bulletin. These corrected estimates were completed exceptionally outside of the usual National Accounts Revisions Policy to provide consistency between GDP and UK trade data. As a result of the corrections included in this publication, estimates are now consistent between UK trade, GDP, and balance of payments publications. 

Data collection changes

Since the UK left the EU on 31 January 2020, the arrangements for how the UK trades with the EU changed. 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. 

We therefore advise caution when interpreting and drawing conclusions from these statistics. Our Impact of trade in goods data collection changes on UK trade statistics: summary of adjustments and the structural break from 2021 article provides more detail. 

International trade in services estimates

From September 2025 until early 2027, International trade in services survey (ITIS) data, which account for approximately 50% of total trade in services, are being processed once per quarter. During this period, the data are based on a survey response rate of approximately 60% to 70%. This enables more focus on improving processing systems and ensuring methods and quality in the future.

The ITIS data that currently inform trade in services estimates are based on benchmarked annual 2023 survey data and quarterly ITIS survey data for periods from Quarter 1 (Jan to Mar) 2024 onwards. We will incorporate benchmarked annual 2024 data in the future, in line with the National Accounts Revisions Policy.

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

Financial sector statistics

Our Financial Services Survey (FSS) transformation will improve the quality of our financial sector statistics. During the period of transformation, starting from Quarter 1 2024, financial services statistics in this release are based on forecasts.

Quality and methodology

More quality and methodology information on strengths, limitations, appropriate uses, and how the data were created is available in our Balance of payments quality and methodology information (QMI).

We will continue to produce our UK balance of payments statistics in line with the UK Statistics Authority’s Code of Practice for Statistics, and in accordance with internationally agreed statistical guidance and standards. This is based on the International Monetary Fund’s Balance of Payments and International Investment Position Manual: Sixth Edition (BPM6) (PDF, 3.0MB), until those standards are updated.

Accredited official statistics

These accredited official statistics were independently reviewed by the Office for Statistics Regulation in December 2011. 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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12. Data sources and quality

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 shows that the three approaches to measuring GDP are closely aligned. However, there can still be uncertainty at the component level, at this stage in the production cycle for 2024 and 2025, until these data have been confronted through the supply and use tables (SUTs) framework. 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 2023, holds constant into 2024 onwards. More information on this is provided in Section 11: Data sources and quality of our GDP quarterly national accounts, 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: January 2025 bulletin to help inform the estimates.

Reaching the GDP balance

Quarterly GDP is a balanced measure of the 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 national accounts dataset.

Net trade

Since the UK left the EU on 31 January 2020, arrangements for how the UK trades with the EU changed. 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.

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. Forecasted data for Quarter 3 (July to Sept) 2025 have now been replaced with ITIS-based estimates.

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 2024, financial services trade statistics in this publication are based on forecasts.

Restarting of Producer Prices publications

We restarted publication of our monthly business prices publications on 22 October 2025. Business prices data with corrected chain-linking methods and updated historical weights have been used in our monthly GDP datasets for Producer Price Indices (PPI), Import Price Indices (IPI), Export Price Indices (EPI), and Service Producer Price Indices (SPPI) in this release. The quarterly SPPI estimates are splined to months for use in monthly GDP calculations.

These updates to business prices data will be incorporated in GDP estimates in line with our National Accounts Revisions Policy, becoming fully integrated for the entire time series in our Blue Book 2026 publication.

Further information on the chain-linking error and the impact of methodological changes in the producer prices dataset are detailed in our Impact of correction to chain-linking methodology used in Producer Price Indices and Services Producer Price Indices: October 2025 article.

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 also the indirectly derived aggregate time series.

This topic is explored further in Section 5: Case study: quarterly GDP of our Assessing residual seasonality in published outputs article, updated on 30 September 2025.

Important quality information

There are common pitfalls in interpreting data series. These include:

• 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: 2025 article, published on 31 October 2025.

Accredited official statistics

These accredited official statistics were independently reviewed by theOffice 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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