Introduction to iXBRL [Technical Tagging Guidance]

This article is an introduction to the principles of tagging a set of accounts.  We've started with a run through of how to choose tags, what to tag, and what to leave.  At the end of the article, we've added a general description of a taxonomy, along with some specific technical concepts that are used when tagging iXBRL.  Where a concept is referred to in the article, you'll be able to head straight to the explanation by clicking the link: e.g. dimensions and tuples.

Over time, we'll work to make this document simpler to understand, based on your feedback, so please, let us know if there is anything that is difficult to follow.  The best way to learn iXBRL is to look at a pre-tagged example in either Accounts Production (the test company) or Accounts Plus powered by Compac (the LTD format), and work through this article.


NB.  Accounts Production handles 99% of the tagging for you, as do accounts produced in Accounts Plus based on the LTD master.  Custom formats in Accounts Plus will need to be tagged, and we'd encourage all users of Accounts Plus to become familiar with the concepts explored in this article.


XBRL - Basic principles of data tagging


In the simplest terms, the XBRL tagging of a report is achieved by matching a tag in the taxonomy to a data item in a financial statement. The data item concerned may consist of a monetary value, an ordinary number, a date, a section of text or some other standard type of data.


For example, if a financial statement contains the line item 'Operating profit £300,000' then the value £300,000 should carry the XBRL tag whose label is 'Operating profit (loss)'. Note that only financial values carry the monetary tag; the description in the human–readable accounts remains untagged and is handled purely as text.


Some textual data in reports has associated tags and should be tagged accordingly. This includes the text of specific declarations, policies and descriptions.

Data which applies to different periods is not represented by different tags. The period is represented by the date context applied to an item (current year and previous year). For example, the same tag is used for operating profit for 2009 as for 2008. Similarly, values at the beginning and end of periods are distinguished by date – not by tag. (The taxonomy contains some tags with labels ending '…start of period' and '…end of period'. This is purely to aid presentation and help users identify tags. These start/end labels reference the same underlying tag.)

The rest of this section provides guidance and rules on the tagging of reports. The following section provides guidance and rules on the entry of data values.

The rules stated below refer to tag in the singular, but they must also be taken to mean combinations of tags, covering both the line item tag and associated dimensional tags, where appropriate.


Choice of tag


A data item MUST be matched against the closest available tag in the appropriate taxonomy, based on the tag's label, position in the presentation view, accounting reference, data type and period type PROVIDED that the use of the element to represent the data item does not introduce a material distortion in the meaning of the business report.

In general, the appropriate tag for a data item should be relatively obvious once the tag is located in the taxonomy. For example, an item in the profit and loss statement described by a company as 'Profit prior to tax' and appearing prior to the tax charge on ordinary activities can obviously be matched against an element in that position in the UK GAAP taxonomy labelled 'Profit (loss) on ordinary activities before tax'. Clearly, the label used for an item in the taxonomy may not exactly match the description used by a company.

The position of a tag in the taxonomy is a strong clue to meaning: for example, a tag listed in the taxonomy under 'Operating costs' is obviously an expense item and not an asset.

However, a tag's position in a presentation view will not necessarily match that of the corresponding item in a company's report. Companies vary significantly in where they choose to place items in their reports. The presentation view in the taxonomy provides guidance on meaning but it is NOT definitional. For example, tags from the primary statements sectionmay be used for line items in the notes of a company report and vice versa. Companies may thus find suitable tags in locations which do not match the particular presentation of their accounts.

Companies may use differing terminology for the same accounting concept. Preparers must not be distracted by terminology and should identify the real meaning of items and tag accordingly.

The basic rule on matching allows some latitude in the application of tags to line items in reports. It seeks a best available match. It recognises that the limited number of tags in the taxonomy cannot represent all the subtlety of meaning which a company may impart through the descriptions and details of formatting which it employs in its financial statements. The latter may be reproduced using Inline XBRL, while tagging is used to convey the general meaning of the item concerned.

Nevertheless, tags should not be 'stretched' in their meaning in order to tag a data item. This would undermine the consistency of tagging across companies.

It is the responsibility of the reporting organisation to make a reasonable judgement on the application of tags in its financial reports.


Scope of tagging


Tags are expected to be applied to the financial sections of reports. Data in the Directors' and Auditors' Report is only expected to be tagged if specific tags exist for this data within the Directors' and Auditors' Report sections of the taxonomy. Other textual reports, such as Chairman's Statement, Financial Review and the like, if they exist, are NOT expected to be tagged.

For example, information on turnover or profit in the Directors' Report need not be tagged since it is assumed this data will be tagged in the financial section of the report. However, information on directors' remuneration may only appear in the Directors' Report and must then be tagged there. Tags for this data exist in the Directors' Report section of the taxonomy.


Significant numeric data


Significant numeric data presented within text in the financial section of a report MUST be tagged with the appropriate numeric tags for that data. It MUST NOT be hidden within a text tag or within an XBRL footnote.

This rule reflects the fact that numeric data may be hidden from analysis software by tagging it as text or dropping it within a footnote. The choice between reporting numeric data as a line item or placing it in a footnote may not be important to a human reader, but it is important when data is encoded in XBRL. Note that this rule is not concerned about how data is displayed in a human–readable presentation – purely about how it is tagged.

Where appropriate tags exist for a section of text and numeric data within the text, then both the text and the numeric data MUST be tagged.


No tag available


If no tag in the taxonomy provides a suitable match for a particular data item, the item may be left as an untagged text line.


Alternative tags


When alternative tags, of different levels of granularity, in the taxonomy match a data item in the accounts, preparers MUST choose the tag which best represents the intended meaning and level of granularity of the data item. In doing so, they MUST abide by the following rules:

  1. If the data item is intended to represent a broad total, then the tag which represents such a total MUST be used. In particular, broad total tags should be used to represent data in primary statements of accounts.
  2. If the data item is intended to represent a detailed breakdown, then the tag which represents that level of breakdown MUST be used. In general, detailed or granular tags should be used to represent data presented in notes to the accounts.

Alternative tags with different degrees of generality will often be available to match an item in a business report. The positioning of the tags within the taxonomy – and thus the level of detail they are intended to represent – will indicate which should be used.


For example, a company may report 'bank interest receivable' in its profit and loss statement. This must be matched against the tag 'Other interest receivable and similar income' in the profit and loss statement section of the taxonomy. It must not be matched against the tag for 'Interest receivable on bank deposits' buried within a breakdown of types of interest receivable in the notes section of the taxonomy. (Clearly, if no other types of interest are received, the two items will have the same value, but the aim of this rule is to ensure that tags representing broad totals are used consistently by different organisations. The alternative tags concerned will often have different accounting references.) Failure to follow this rule will mean that tags for expected totals will be missing.


By contrast, for example, a company may report 'bank overdrafts' in a note showing a detailed breakdown of liabilities. The taxonomy may contain tags for such a breakdown representing (a) 'bank borrowings and overdrafts', (b) 'bank borrowings' and (c) 'bank overdrafts'. If the company does not have any bank loans, it may appear that the company line item can be matched against either (a) or (c). In this case, however, the data item must be matched against (c) – the tag in the breakdown which specifically matches the meaning and level of granularity of the line item.

Similarly, a company may report 'corporation tax paid' as the sole tax related item in its cash flow statement. This must be matched against the tag 'Taxation expense (credit)' shown in the taxonomy cash flow statement. The tag 'UK corporation tax paid' exists to tag such an item when it appears as part of a detailed breakdown in the notes to cash flow, alongside other tax payments and receipts.


Unique application of tags


Apart from in the special case of tuples, the value assigned to each tag for a single context in an XBRL report MUST be unique. The same tag MUST NOT be assigned to different data values with the same context.

The context of an item means the period, entity and dimensions to which it applies.

This rule means that the same tag must not be used for different data in the same report. For example, if the 'Operating profit (loss)' tag is attached to a value of £1 million for the financial year 2008, it must not also be attached to a value £1.5 million for the same period and company.

This rule ensures the consistency of reports from the point of view of both accounting and tagging and if not followed will result in an error being return from the Government Gateway whilst attempting to file.

Clearly, the same tag may be reused for different time periods and for different dimensions, such as continuing operations, joint–ventures and the like.


Repetition of tags within tuples


Tags within tuples may be used multiple times for the same context within an XBRL report, but in this case they must be reported in different occurrences of the tuple.

This rule reflects the normal functionality of tuples.


Tagging of multiple occurrences of data items


If the same data item appears in different places in a financial section of a report then all occurrencesof that data item must be tagged, even if different scaling applies to some occurrences. This rule ensures that data is consistently reported in XBRL and discrepancies between human readable andXBRL reports do not occur.


For example, the same accounting line item may appear both in a primary statement and in a note to the accounts. Both occurrences must be tagged.


This rule ensures that data in financial reports is filed consistently and enables a range of basic validity checks. It helps to ensure that different numbers for the same thing do not appear in different places within a report. It is important, among other things, for assurance on accounts.

This rule concerns the financial section of accounts, not the textual reports which precede the financial section.


Use of 'generic' tags


A small number of dimensions contain 'generic members' to represent expected breakdowns of information. For example, the 'Entity officers' dimension includes Director 1, Director 2, etc. as well as Chairman, Chief executive and the like.

Other dimensions with generic members include:

  • Acquisitions: Acquisition 1, Acquisition 2, etc.
  • Joint–Ventures, Associates and Subsidiaries: Associate 1, Associate 2 etc.
  • Business and operating segments: Business segment 1, Business segment 2 etc.
  • Pension schemes:Pension scheme 1, Pension scheme 2 etc.

The identification of dimensions with generic members should be obvious. In case of any doubt, these are dimensions whose members have a sequence of numbers after their names.

All of these dimensions are attached to a name and / or description tag so that the identity of a particular dimension member may be defined.

For example, there is a 'Name of entity officer' tag which is linked to the 'Entity officers' dimension. Similarly, there is a 'Name of defined benefit scheme' tag which is linked to the 'Pension schemes' dimension.

The following rules apply to the use of generic dimension members.

When a generic dimension tag is used in an XBRL report the associated name and/or description tag MUST be used in combination with that tag to provide a human readable identification.

For example, generic dimension tags like Director 1, Director 2, Acquisition 1, Acquisition 2 must be identified using the appropriate name tag in combination with them.

Generic dimension tags MUST be used consistently within a report. Any data tagged with a particular generic dimension tag MUST relate uniquely to that single dimension tag.

For example, if Director 1 has been identified as Joe Bloggs, then the Director 1 dimension tag must be used consistently throughout a report to apply only to data related to Joe Bloggs. A single generic dimension tag must not be used to identify different things within a single report.

The number of generic tags defined in each dimension should be more than sufficient for most purposes. For example, the 'Entity officers' dimension allows up to 80 directors to be identified, since each of the 40 generic tags for director may be separately identified as either executive or non–executive.

In the very rare cases where the number of generic dimension tags is insufficient, preparers may use text in Inline XBRL to report the data which cannot be tagged.


Use of 'fixed value' tags


A small number of tags have a predefined fixed value of 'nil'. They have their effect simply by being included in an XBRL report in combination with an appropriate dimension tag. They do not contain any value in the XBRL report.

An example is 'Country of formation or incorporation'. To represent country of incorporation, this tag should be included in an XBRL report in combination with the appropriate dimension tag from the 'Countries' dimension. This ensures unambiguous identification of the country concerned.

Another example is 'Director signing report' in the Directors' Report section. This tag should appear in combination with the dimension tag identifying the director concerned from the 'Entity officers' dimension. (The name of the director is defined separately by the 'Name of entity officer' tag used in combination with dimension tag for the director.)


Use of 'free–text comment' tags


Free–text comment tags MUST only be used to cover supplementary comment in the specific area to which they apply. They MUST NOT substitute for specific tags where the latter would be appropriate.

For example,free–text comment tags should be used to tag the general explanation which might appear at the bottom of a note to the accounts, for which no other suitable tag exists.


Use of tags for 'Other…' data


A number of tags represent a residual amount from a list of items. An example is 'Other creditors'.

These 'Other' tags may be used to tag items which are genuinely labelled as other / residual in a company report or they may be used to tag a single remaining item in a list for which no other suitable tag exists. However, a single other tag MUST NOT be used to tag multiple different items for the same period. This would break above on the unique application of tags. If multiple items exist for which no tag is available, they may simply be reported as text with no tagging.


Compulsory tags


The following tags MUST be used in XBRL accounts to aid in processing:

  1. Entity current legal or registered name
  2. Companies House registered number (where applicable)
  3. Company dormant / not dormant
  4. Company trading / not trading
  5. Start date for period covered by report
  6. End date for period covered by report
  7. Directors report date of signing
  8. Directors signing directors report
  9. Balance sheet date
  10. Balance sheet date of approval
  11. Balance sheet approving directors / authority
  12. All declarations under 'Statements in Directors' Report' and 'Directors' or entity's declarations', which apply to the entity concerned.

The rules on the directors' report apply to the equivalent of this report in organisations which do not publish a directors' report. For example, they apply to the trustees' report provided by charities.


Tagging of comparative data


In general, comparative data for preceding periods in financial reports MUST be tagged, just as data for the most recent period is tagged. This rule includes previous period data for which no current data is published. However, HMRC is NOT asking for previous year comparatives in the first year of mandatory filing for the purposes of accounts included as part of the CT600 return.

The exception to the general rule for the first year of mandatory filing to HMRC from 31 March 2011 to 31 March 2012 reflects the fact that mandatory tagging did not apply prior to 31 March 2011. Preparers are still encouraged to provide tagging of comparatives, but it is not mandatory to do so.


Distinction of company and group data


The dimension tags 'Consolidated' and 'Company [default]' exist to distinguish group and company data. Their use will normally be straightforward, with company being the default. In some cases, however, an organisation may present some data in its accounts as applying to both group and company. For example, such combined accounts may show separate balance sheets for the group and the company, but a single table for tangible assets, with the same tangible asset values applying to both group and company. The general rule for handling such cases in Inline XBRL is:

When group and company data in a financial report is being tagged, a data item which represents a value for both the company and the group MUST be tagged twice: once using the appropriate 'Consolidated' dimensional tag to identify the data as pertaining to the group and once without a tag for consolidation, indicating that it pertains to the 'Company [default]'. Clearly, other tags attached to the data item will be identical.

This double tagging is necessary to identify the correct meaning of the data to software.

Note, however, that up to 31 March 2013, HMRC has said that tagging of group data is NOT mandatory. Preparers may file group data in ordinary text format, without tagging.


'Not applicable' tag


A special tag, 'Not applicable', is defined as a dimension member in a number of dimensions. When included, it is always the default tag in the dimension. Its full label is 'Not applicable [default]'.

This tag automatically causes the dimension concerned to be ignored, except when a preparer actively uses a tag from the dimension. It exists for technical reasons and simplifies the design of dimensions and the work of tagging.

Accounts preparers should never need to use this tag when tagging data and effectively can ignore it.


Positive and negative values


The correct positive and negative sign must be applied to data values in an XBRL report. This sign is determined by XBRL rules based on the taxonomy. It is NOT necessarily the same as the sign which is used in the human–readable view of a report. The latter is controlled by the preparer and will depend on the particular conventions which a company follows. (Signs can be transformed between the underlying XBRL data value and the human–readable presentation using features of Inline XBRL.)

Preparers of XBRL reports MUST follow the rules below when entering XBRL data values:

  1. Data MUST always be entered as positive UNLESS rule (b) below requires otherwise.
  2. Where data may be positive or negative, the label will indicate the correct sign of the item. Labels will use brackets around terms to show what data should be entered as negative.

Examples of sign indicators in labels are:

  • Operating profit (loss)
  • Net current assets (liabilities)
  • Net cash flow (outflow) from financing
  • Funds (debts) acquired with subsidiaries

If a company reports an operating profit, it will thus enter the value of the profit as positive. On the other hand, if it reports a loss, it will enter the value of the loss as negative. Similarly, it will enter funds acquired with subsidiaries as positive, but debts acquired as a negative value.

The taxonomy also allocates debit / credit balance indicators to some monetary tags. These may help guide userson the correct sign, but they only sensibly apply to income and asset / liability data and the wording of labels always takes precedence in determining sign.


Tagging of text


A large range of tags of string data type are available for tagging of text. These range from tags for simple text, such as entity name, through to longer declarations or descriptions, such as tags for accounting policies. Dimension tags may apply to text tags in exactly the same way as numeric tags. For example, the policy on a particular class of tangible assets may be identified by combining the 'Tangible fixed assets policy' tag with the appropriate dimension tag for that class.

Any text, including paragraphs, numbers and other formatting, may be tagged with a text tag. However, preparers should note the rule above on not burying significant numeric data within a text tag. Where it is necessary to tag a section of text which includes numeric data for which a tag is available, preparers must tag the numeric data as well as the section of text concerned.

Preparers must make a reasonable judgement on precisely what portion of a particular textual statement should carry a tag. In most cases, this should be obvious. The granularity of text string tags has been defined, as far as practical, to accord with likely company textual statements.


XBRL Concepts



Taxonomies are at the heart of XBRL, they define the individual tags that identify specific items of business data.

The taxonomy used within Compac is UK GAAP; this represents typical reporting by companies under UK GAAP, including FRSSE regulations. A special extension to the UK GAAP taxonomy exists for charities.

The UK GAAP taxonomy contains a number of common components, including modules covering the Directors’ Report, Auditors Report and standard business data.It also includes information on HMRC minimum tagging requirements.

XBRL UK are responsible for the maintenance of the taxonomy; the tags within Compac are made available exactly as they are supplied by XBRL UK. Over time, it is expected the taxonomy will be expanded to cover items which may be reasonably commonly used but are missing now. The taxonomy will also be amendedto improve its accuracy, clarity and ease of use.

Comments and questions on the UK GAAP taxonomy and use of XBRL are welcome. Let us know by emailing


Taxonomy features and content

The taxonomy includes a range of features to identify tags, to aid ease of use and to enable software to process XBRL data efficiently.  It also contains special features to cope with different aspects and formats of reporting. The main features are:




The human-readable labels on tags provide their main definition – as far as possible, they uniquely identify the tag concerned.  Labels in taxonomies are typically longer and more explicit than descriptions of line items in financial reports.  For example, a taxonomy label will say ‘Tax on profit or loss on ordinary activities’ not just ‘Tax’. 




The UK GAAP taxonomy is presented in the same format as the financial reports, thus mimicking the basic structure of accounts, with primary statements followed by notes and detailed disclosures. 

The position of a tag in the presentation hierarchy of the taxonomy should give a strong indication of its use and meaning.  For example, ‘Tax on profit or loss on ordinary activities’ will appear in the profit & loss section of the taxonomy between profit before tax and profit after tax.  Some tags may appear in multiple places in the presentation view because they may typically be reported in different positions in accounts.

The presentation of the taxonomy is a ‘common denominator view’ which mimics the typical positioning of items in accounts.  It is intended purely to help users locate and identify tags in the taxonomy.  It does not determine how items are presented in accounts filed in Inline XBRL – that is determined entirely independently by the preparer.  Nor does it represent how data may be aggregated.  For example, some items located within notes in the taxonomy may well be included in primary statements in some company accounts, or vice versa. 

Taxonomy presentation views do not attempt to represent all possible layouts of accounts.  Given the huge variation in formatting of UK accounts, this would not be practical.  The presentation view of the taxonomy is very unlikely to match exactly the organisation of any individual set of accounts. 

In order to represent all the main data items which companies may include in their business reports, the taxonomy contains thousands of tags and inevitably appear larger and more complex than an ordinary set of accounts. 

The existence of a tag in the taxonomy does not mean that it will necessarily appear in the financial statement of a particular company.  Preparers are not expected to adjust the content of their accounts to fit the taxonomy.

Because taxonomies are presented in hierarchies, with more detailed tags appearing ‘below’ major ones like totals, the precise ordering of tags may not match that of line items in typical accounts.  The hierarchy of tags in taxonomies is intended to enable efficient presentation on screen. 

In summary, the presentation view is intended to help taxonomy users to find tags.  Preparers remain free to determine the content and formatting of their own financial statements.

Headings and other information items


The taxonomy includes a range of heading items to help organise the presentation view or to provide explanation.  Examples include ‘Profit and loss account’ and ‘Specific accounting policies’.  These headings cannot be used in the tagging of accounts.  In the UK GAAP taxonomy, they end with a word in square brackets, such as [heading] or [explanation].

The screen shot below shows a presentation view of part of the UK GAAP taxonomy, including several heading items.  This gives a typical view of the arrangement of tags in a presentation hierarchy. 


Part of the Profit and Loss statement from the UK GAAP taxonomy.  The + sign indicates that more tags exist as children of the tag concerned.


Data types


Taxonomy tags are assigned a ‘data type’ to identify their meaning and role and to assist in processing XBRL data.  The data types used in UK taxonomies are:


+            Monetary  (to represent monetary values)

+            String  (to represent ordinary textual information)

+            Decimal  (to represent or ordinary numbers)

+            Integer  (to represent whole numbers)

+            Shares  (to represent numbers of shares, options and related instruments)

+            Date  (to represent specific dates in a yyyy-mm-dd format)

+            PerCent  (to represent percentage values)

+            PerShare  (to represent values per share)

+            URI  (to represent URIs)

+            Boolean  (to represent true / false statements)

+            Domain item  (part of a dimension, explained later in this document)

+            Fixed item  (special text item with fixed value, explained later in this document)


The vast majority of tags are either monetary or string.  The use of these types helps to ensure correct entry of data in XBRL reports and more effective verification by software.


For example, the tag 'Operating profit (loss)' is a monetary type, whereas 'Basis of audit opinion' is a string.


Dimensions and ‘tuples’


Dimensions and tuples are two important technical features of the taxonomy, which allow data that is often reported in the form of tables to be handled efficiently in XBRL.  They are described in separate sections below.


  • Period type


All tags are identified as being either related to an ‘instant’ (i.e. a stock) or a ‘duration’ (a flow).  This relates to the period at which or over which they are measured.  This information helps to identify tags and ensure correct data entry and validation of reports in XBRL.


  • Balance type


Some monetary tags may be identified as either a ‘credit’ or ‘debit’ balance type.  This helps to confirm their identity and the correct sign on their monetary values. 


  • Names


The ‘name’ of a taxonomy tag is its unique computer-readable identifier.  The name is derived from the tag label to make it easy for to read and decipher underlying XBRL files.  An example is ‘OperatingProfitLoss’ which is the name for the tag labelled ‘Operating profit (loss)’.




Taxonomy dimensions represent the different forms in which financial data may be reported.  Typically, they may be thought as representing the columns in a financial table, while ordinary tags represent the rows. 

For example, ‘Operating profit (loss)’ may be reported under UK GAAP for continuing and discontinued operations, before or after exceptional items, for subsidiaries, joint-ventures, associates, geographic and business segments and so forth.  It is not practical to represent all these different forms of operating profit by individual tags in the taxonomy.  Instead, standard breakdowns of this type are represented in the taxonomy by dimensions

In the UK GAAP taxonomy, dimensions are used, among other things, to distinguish: 


+            group from company data

+            continued and discontinued operations

+            classes of tangible fixed assets

+            classes of intangible assets

+            classes of provisions

+            business operating segments

+            geographic operating segments

+            subsidiaries, joint-ventures and associates

+            restated information, including most prior period adjustments

+            before and after adjustments for exceptional items

+            acquisitions / business combinations

+            a wide range of data related to financial instruments

+            individual pension schemes

+            individual directors

+            paid and proposed dividends


Each dimension includes a range of dimension member tags.  For example, the tangible assets classes dimension in UK GAAP contains tags for ‘land and buildings’, ‘vehicles, plant and machinery’ and so forth. 


Dimension tags are always used in combination with ordinary line item tags.  For example, the line item tag ‘Gain(loss) from disposal of tangible fixed assets’ is used in combination with the tangible assets dimension members.  This enables gains and losses from disposals of different classes of assets to be tagged accurately. 


Some dimension tags may be used simultaneously together.  For example, dimension tags for continuing and discontinued operations may be used in conjunction with the dimension tags representing business operating segments. 


The taxonomy defines the dimension tags which may be used with each ordinary line item tag and which dimension tags may be used simultaneously.  In other words, the taxonomy predefines the forms of financial tables which can be represented by the taxonomy.  In practice, it enables a far richer set of tables than will normally be needed in an individual company report.  However, it does not permit line item tags to be used with inappropriate dimensions. 


Preparers carrying out manual tagging must be aware of available dimensions and use these correctly.  To help inform users and ensure they are aware of dimensions, individual tags also list available dimension members.


Most dimensions include default members, which are considered to apply if no specific dimension member tag is applied.  For example, the default member of the tangible fixed assets classes dimension is ‘All tangible fixed assets’.  Any tangible assets line item tag which is not used in combination with a specific tangible asset dimension member is thus considered as representing the total across all classes.  All default tags include the word [default] in square brackets at the end of their label.


All usable line item tags in the taxonomy are tied to a number of dimensions which may be used in conjunction with them.  At the very least, line item tags are linked to the basic dimensions distinguishing group and company data and restated information.  The defaults for those are ‘company’ and ‘original stated’, respectively.


In practice, most line items in accounts will probably be reported using defaults, without a need for explicit tagging with dimension tags. 


For example, many companies reporting under UK GAAP will be able to report 'Total dividend payment' without needing to use the dimension tags available to distinguish paid from proposed dividends and different classes of share.  The latter only need be used when such distinctions are required.  The default on the paid and proposed dimension is the total of paid and proposed and the default on the shares dimensions is all classes and types of share. 




Tuples are used to group tags in the taxonomy which (a) may be used repetitively in an XBRL report and (b) can only be properly understood when used in conjunction with one another.  Tuples are typically used to handle narrowly defined, detailed information. 


For example, information on specific loans to directors is represented by a ‘Specific advance or credit, directors’ tuple.  This tuple contains tags which represent (i) a description of a specific advance and (ii) its monetary amount.  These tags may be reused, as a grouping, multiple times to tag different loans to directors.  Clearly, the monetary amount of such a loan cannot be fully understood unless it is coupled with a description.


Another example of a tuple is information on specific loans from banks.  Tags for information on the loan and its amount are contained in a tuple so that they can be repeated to describe different loans.  The screen shot below shows this tuple.




Example of a tuple.The tuple item itself, ending in '…[grouping]' is not used in tagging,but the tags contained in the tuple (i.e. underneath the heading) may be.


Tuple items themselves just act as the parent of a group and are not used in tagging.  It is the ordinary items within the group which are used as tags.  Tuples can be identified in the taxonomy through their heading element which always carries the term [grouping] in square brackets at the end of the label.


There is no limit on the number of times which tags contained in a tuple may be repeated in an XBRL report.


A special case of tuples is those which contain only one tag.  An example is the tuple ‘Accounting policy changes [grouping]’ which contains only the tag ‘Description of change in accounting policy and its impact’.  The purpose of containing this tag within a tuple is to allow it to be used multiple times in a report to tag different descriptions of changes in accounting policies. 


Scope of taxonomies


The UK GAAP taxonomy provides tags for financial data items whose appearance in company reporting is reasonably typical or predictable. They do not define tags for every eventuality or for unusual or company-specific line items. 


The taxonomies do not provide tags to represent large blocks of text, such as the full Directors’ Report.  XBRL is intended to represent discrete items of information, so that these may be analysed by software or be easily found, collated and compared.  For example, there are tags to represent individual accounting policies, but there is no tag to represent all policies as a whole.


If no suitable tag is available to represent a particular item of data in a financial report, then the item may be left untagged and simply represented by ordinary text in Inline XBRL. 


Tagging requirements


In principle, every data item in a company report should be tagged if an appropriate tag (or combination of tags) exists for that item in the relevant taxonomy. 

However, for the first two years of XBRL mandated use, up to 31 March 2013, HMRC has set a reduced tagging requirement to help users adapt to XBRL and to limit effort involved in manual tagging and in software development.  Under this approach, users have to use only a minimum set of tags.  This minimum set represents about a third of the available tags in the UK GAAP taxonomy. 

The minimum tagging set is clearly highlighted within Compac; where the full taxonomy is loaded, the minimum tags appear in black text, the remaining optional tags are grey. 

For your information, the full tagging set has been applied to the Compac limited company master layouts; these tags can be applied to your own layouts provided they are the same as the master, otherwise, they may be used as examples for you to study before attempting your own tags. 2013, HMRC has set a reduced tagging requirement to help users adapt to XBRL and to limit effort involved in manual tagging and in software development.  Under this approach, users have to use only a minimum set of tags.  This minimum set represents about a third of the available tags in the UK GAAP taxonomy. 

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    Christopher Burrows

    This has been extremely useful. The Compac tagging process is great and we are now ready to file our first XBRL accounts with a company tax return.

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