The reason for having a Primary Financial Statements (PFS) in your report in the first place, is to provide comparability with previous years and other companies. If you want to provide detailed information from the notes, you are free to provide correct and detailed tagging of these, but you will be looking at some heavy work that very few technical readers (if any) will make use of. The comparability of the financial statements in your report will be diminished year-over-year by elevating note information, while also increasing your workload and costs at the same time.
Example:
In case a company states e.g. “Revenue” in their income statement and additionally states in their notes that revenue (currently) only consists of e.g. revenue from the sale of goods, certain customers/auditors' demand for tagging the “Revenue” in the income statement as “RevenueFromSaleOfGoods” instead of the broader “Revenue” concept.
The justification:
The RTS states “When marking up disclosures, issuers shall use the core taxonomy element with the closest accounting meaning to the disclosure being marked up”. Some lean on the “...closest accounting meaning...” to be whatever is behind the “Revenue” line above and tend to disregard the “...to the disclosure being marked up” part.
The problems:
By doing the above, the company/auditor elevates note information to the PFS whereafter the technical part of the iXBRL file doesn’t have a PFS/note structure anymore (and thereby also contradicts ESMA guidance). It also opposes ESMA’s chosen compromise with detailed tagging of the PFS and block tagging of the notes, as detailed parts of the note information would already be provided as PFS information.
The customer could very well also have e.g. revenue from services next year where the tagging will then have to change, affecting comparability year-over-year both between the company’s own reports and other issuers.
In the example above, the customer’s meaning of “Revenue” could likely change year-over-year (and could – from a data perspective – potentially become unreliable). It would create an unnecessary need for constant maintenance and review with equally unnecessary costs.
The objective of XBRL is to give a technical reader the same experience as a human – but in a structured format where information can easily be located and understood internationally. You are required to provide a detailed, technical replication of your primary financial statements and to provide additional information by block-tagging the notes. Furthermore, you are required to stay true to the structure; not to leave out vital and comparable PFS information, and provide a limited amount of detailed note information.
The example above is similar to e.g. tagging “Right-of-use assets” as “RightOfUseAssetsThatDoNotMeetDefinitionOfInvestmentProperty”, “Other finance costs” as “InterestExpense”, “Other financial assets” as “FinancialAssetsAtFairValueThroughProfitOrLoss” and similar. Related to the “Revenue” example at the top, perhaps we should ask ourselves: would it be beneficial to change the text in the income statement to “Revenue from sale of goods” to give the technical and visual readers the same experience? Chances are that you want to keep the text to: a) leave room for adding different kinds of revenue and/or b) keep comparability with other companies. Either way, tagging it as anything other than “Revenue” would not be aligned with the general and overall intention of XBRL.