Your annual report may be the same in London and the EU. Your UKSEF filing and ESEF filing processes are not. Taxonomies, auditor involvement, validation rules and submission systems now differ, creating additional complexity for dual-listed companies.
Since Brexit, the UK and EU electronic reporting rules have drifted apart. The underlying technology is still the same: an XHTML report with Inline XBRL (iXBRL) tagging. But the rules on taxonomies, audit, filing and timing now differ. For dual-listed companies, those differences decide how many files you prepare, who checks them and where they go.
Here’s what differs between the two regimes, and how to plan for both.
Understanding UKSEF and ESEF
- ESEF is the EU’s electronic reporting format for issuers with securities on EU regulated markets, set out in the ESEF Regulation and overseen by ESMA and national authorities.
- UKSEF is the term commonly used for the UK’s equivalent, set out in the FCA’s rules (DTR 4.1). Strictly, UKSEF is the FRC’s approach for using the ESEF taxonomy alongside the FRC Taxonomy Suite in one report.
The UK kept ESEF when it left the EU, then moved the rules into the FCA’s own rulebook. The FCA says the substance for companies hasn’t changed.
UKSEF vs ESEF: Key Differences at a Glance
The goal isn’t managing two reports. It’s making one reporting process satisfy two regulators.
| EU (ESEF) | UK (FCA) | |
| Who it applies to | Issuers with securities on EU regulated markets | Issuers with transferable securities on UK regulated markets, such as the LSE Main Market |
| Rulebook | ESEF Regulation (EU) 2019/815 and ESMA’s Reporting Manual | FCA DTR 4.1, plus FCA Technical Note 507.2 on accepted taxonomies |
| Report format | XHTML | XHTML |
| What gets tagged | IFRS consolidated statements in detail, notes block-tagged | IFRS group statements in detail, notes block-tagged. |
| Taxonomy | ESEF taxonomy, updated by ESMA | A generally accepted taxonomy: the ESEF taxonomy, used alone or via the FRC’s UKSEF approach |
| Auditor opinion on tags | Required under EU law | Not required; voluntary assurance available |
| Where you file | The officially appointed mechanism in your home member state | The FCA’s National Storage Mechanism (NSM) |
| Deadline | Four months after year-end | Four months after year-end |
| Central access | ESAP, collecting data since July 2026 | NSM, publicly searchable |
Four Differences Dual-Listed Companies Should Know
1. Taxonomy Choice
In the EU, you tag with the ESEF taxonomy. In the UK, the FCA accepts the ESEF taxonomy, either on its own or via the FRC’s UKSEF approach.
UKSEF adds UK-specific tags from the FRC Taxonomy Suite, including the company’s registered number and balance sheet date. Those let one tagged file also serve as a Companies House filing.
For dual-listed companies: The ESEF taxonomy is the common ground between the two regimes. Unless you need the additional Companies House tags, using the ESEF taxonomy across both filings is often the simpler approach.
2. Auditor Involvement
This is the biggest practical gap.
- EU: EU law requires statutory auditors to give an opinion on whether the financial statements comply with ESEF.
- UK: The UK government has confirmed there is no requirement in UK law for the auditor to report on ESEF compliance. Companies can choose voluntary assurance under ISAE 3000.
For dual-listed companies: If your EU filing needs an auditor opinion, your tags will face audit scrutiny anyway. Plan one review process that meets the stricter standard.
3. Filing and Validation
UK filers submit through the FCA’s Electronic Submission System to the National Storage Mechanism (NSM).
The FCA validates every file. If errors appear, it rejects the file, and you must resubmit as a new case. You also can’t use a primary information provider to meet the structured filing obligation.
EU filers submit to the officially appointed mechanism in their home member state. National authorities then check filings against ESEF requirements.
For dual-listed companies: That’s two submission systems, two sets of naming and packaging rules, and two validation checkpoints.
4. Version Timing
The two regimes update on different calendars.
| EU (ESEF) | UK (FCA) | |
| Reporting Manual | 2025 version | 2025 version, from 14 August 2026 |
| Taxonomy for FY2026 | 2025 ESEF taxonomy, mandatory | ESEF 2024, alone or via UKSEF, per Technical Note 507.2; FCA to accept ESEF 2025 later in 2026 |
For dual-listed companies: The rulebooks now match, but the taxonomy lists don’t. Check both regulators’ accepted versions before you start tagging.
Can a Single Report Meet Both Regimes?
Sometimes. The FCA accepts the ESEF taxonomy, so one ESEF-tagged report can be your starting point. But for FY2026, the taxonomy gap may force two versions of the file.
Run these four checks first:
| Check | Why it matters |
| Is the same taxonomy version accepted in both places at filing time? | Update cycles differ, so a version one regulator accepts may not be on the other’s list yet |
| Do you need a Companies House filing from the same file? | If yes, you need FRC Taxonomy Suite tags under the UKSEF approach, which go beyond the ESEF taxonomy |
| Does the package meet both sets of naming and format rules? | Each submission system has its own technical guidelines |
| Has the auditor reviewed the tags to EU standards? | The EU opinion requirement sets the bar for both filings |
Do UKSEF and ESEF Both Apply to Your Company?
The answer depends on where your securities trade and your regulatory status.
| Your situation | What to expect |
| UK company listed only on a UK regulated market | FCA rules apply. File to the NSM using the ESEF taxonomy, alone or via UKSEF. |
| UK company also listed on an EU regulated market | FCA rules for the NSM, plus ESEF in your EU home member state |
| EU company also listed on a UK regulated market | ESEF in your home member state, plus the FCA’s rules, unless a DTR 4.4 exemption applies |
These are general patterns, not legal advice. Exemptions, home-state rules and auditor requirements vary, so confirm your position with your advisers and the relevant regulators.
5 Ways to Simplify Dual-Listed Reporting
- Map your obligations early. List every market, regulator, taxonomy and auditor requirement before year-end.
- Pick one tagging baseline. Use the ESEF taxonomy as your common core unless you need UKSEF’s Companies House tags.
- Tag once, check twice. Run validation against both the ESMA and FCA rules on every draft.
- Review against the stricter standard. Build your tag review around the EU auditor opinion, even for the UK file.
- Test the UK submission. The NSM lets you submit for validation only, so test before your filing date.
An AI-powered disclosure management platform turns these five steps into one workflow. You tag once, validate against both ESMA and FCA rules in the same place, and keep a full review trail for your auditor. Two regimes, one process.
UKSEF vs ESEF: FAQs
1. What is the key difference between UKSEF and ESEF?
Both use XHTML and iXBRL. They differ on taxonomy choice, auditor involvement, filing systems and update timing.
2. Is UKSEF mandatory?
No. UK issuers must file in a structured format, but they can tag with the ESEF taxonomy alone or use the FRC’s UKSEF approach. UKSEF is useful if you also want the file to serve Companies House.
3. Can I use the ESEF taxonomy for my FCA filing?
Yes. The FCA accepts the ESEF taxonomy, used alone or via the FRC’s UKSEF approach. Check Technical Note 507.2 for the accepted versions.
4. Does the FCA accept the 2025 ESEF taxonomy?
Not yet. The FCA says it will start accepting the 2025 ESEF taxonomy later in 2026; Technical Note 507.2 (July 2025) lists only ESEF 2022 and 2024. Check the current version before you start tagging.
5. Does ESAP cover UK filings?
No. ESAP is an EU platform. UK filings are available through the FCA’s NSM.
