ESEF - lessons learned from the first filings

by Jon Rowden iXBRL leader

Email +44 (0)7715 457437

First-time European Single Electronic Format (ESEF) reporting is now well underway, with voluntary or mandatory filings for December 2020 annual reports being made in many countries. Over the next year, activity will only increase, so it seems helpful to share some early perspectives from our network of ESEF experts. Here’s what we’ve learned so far:

Do a dry run on the prior year’s annual report. The more that can be done before the “red zone” weeks just before the filing is due, the better. A dry run helps identify and solve problems early and we haven’t met a client yet that regrets doing this.  

Year end timetabling is key. Even with a dry run completed, having an agreed plan of who will do what, and when, leads to a slick completion process. Outsourced tagging providers, management review and any involvement of auditors can lead to many hand-off events that are best choreographed in advance.

Not all errors are created equal, but they all have to be looked at. Many errors just have to be fixed - a broken file won’t get through a regulator’s digital gateway. But other problems that are flagged up by automated checks can turn out not to be problems at all. Something called the calculation linkbase is often at the root of these false alarms. Reserve time in the process for addressing errors and keep an open mind.

Rendering the human-readable document needs care. Converting a file to XHTML isn’t always straightforward, with page breaks and page numbers a well known source of problems.  

All the attributes of a tag are important. Choosing the right tag from the taxonomy is crucial and often involves judgement, but that’s not the end of the story. Dates, scale and currency attributes can all go wrong. Getting the positive/negative sign attribute right takes particular care in statements of cash flows or changes in equity.  

Test gateways would be a big help. If regulators could make this happen in a secure way, it could accelerate the date ESEF information becomes available to investors and other stakeholders.

Bank the learnings and improvements. Those of us who have worked on new XBRL mandates recognise a familiar theme: rough edges, whether they relate to software, process or understanding, are currently being smoothed off. Capture these learnings for next year’s filing process. 

Our ESEF experts would love to hear about your Year 1 experiences. If you are currently in the planning phase, and would like to know more, please reach out to us at

by Jon Rowden iXBRL leader

Email +44 (0)7715 457437