A Guide for Accounting Firms: Becoming an XBRL Reporting Partner

Organisations around the world are increasingly required to submit financial and regulatory information in structured digital formats such as XBRL and iXBRL.

Producing these filings requires reports to be tagged, checked against the relevant taxonomy and validated against the applicable filing requirements before submission. The process requires skills that most in-house finance teams only need once a year, so many companies rely on an external specialist.

This guide explains what an XBRL reporting service involves, how firms can package and deliver it profitably, and how platforms such as CoreFiling’s Seahorse can reduce technical burden and accelerate adoption.

What Is an XBRL Reporting Partner?

An XBRL reporting partner helps organisations to meet their digital reporting obligations, either by tagging and validating structured reports on the client’s behalf, or by licensing the software needed for the client to manage the process internally.

In both models, the partner holds the taxonomy expertise so the client does not have to build and maintain that knowledge in-house.

Most XBRL reporting partners are either accountancy firms that offer the service alongside audit and financial reporting work, or specialist providers focused exclusively on structured reporting.

XBRL (eXtensible Business Reporting Language) and Inline XBRL Explained

XBRL is a global standard used for digital business reporting. It allows figures and narrative statements to be tagged with specific XBRL concepts defined in a taxonomy. Inline XBRL (iXBRL) combines those tags with a human-readable report, enabling a single filing to be used by both people and software systems.

Both formats are widely used across regulatory reporting programmes. For accounting firms, the important takeaway is that both XBRL and iXBRL reporting require specialist knowledge of taxonomies, validation rules and filing requirements, creating an opportunity to provide reporting services and support to customers.

Our guide to XBRL and iXBRL explains the technical differences in more detail.

Why Accounting Firms are Adding XBRL Services?

Accounting firms already understand the accounts, reporting deadlines and client teams behind these filings. For many firms, XBRL represents a natural extension of existing advisory services while also creating a source of recurring revenue.

Recurring Demand for Specialist Expertise

Most organisations only encounter a particular reporting mandate periodically. As a result, it can be difficult to retain detailed knowledge of the taxonomy, extension concepts, anchoring conventions and validation rules between reporting seasons.

Reporting partners fill that gap by developing expertise across reporting formats and programmes. A team that supports hundreds of reports each season can typically resolve tagging and validation questions far more quickly than an internal team relearning the process under deadline pressure.

A Service That Becomes More Profitable Over Time

Firms can choose a model that matches their clients’ needs and their own level of involvement:

• Per-Report Fee: The firm tags and validates the report, then returns a filing-ready document for a fixed price.

• Software Resale and Support: The client licenses the platform through the firm and completes the tagging in-house, with training, review and taxonomy support provided as required.

• Review and Assurance: The client, or another provider, prepares the tagged report, and the firm checks it independently before submission or sign-off.

The first reporting cycle carries most of the setup cost, including taxonomy mapping, process design and client education. Subsequent engagements can reuse much of that work, reducing delivery time and improving the margin on a recurring fee.

More Mandates Mean More Opportunities

Structured reporting extends far beyond any single filing programme. XBRL and iXBRL are used by millions of companies globally, including for company accounts, tax reporting, prudential returns and regulatory disclosures.

As new mandates emerge, organisations frequently seek specialist support to understand and comply with new requirements. Firms that build expertise early are better positioned to support new reporting programmes, win additional work, and strengthen long-term client relationships.

What the Service Actually Involves?

An XBRL reporting service combines accounting judgement with a controlled production process. While software automates much of the preparation and validation work, the reporting partner remains responsible for the tagging decisions, review, and delivery of a filing-ready report.

XBRL Taxonomy and Structured Data Requirements

Tagging therefore involves more judgement than simple data entry. Multiple taxonomy concepts may appear suitable for the same disclosure, and the tagger must select the concept that best reflects the company’s reporting.

When no suitable standard concept exists, an extension concept may need to be created and anchored to the closest taxonomy concept. These decisions have a direct impact on the quality and comparability of the reported data and are often areas where first-time filers require additional support.

Tagging, Validating and Filing for Clients

Once the client provides the draft report, the reporting partner takes it through a structured workflow before it is ready for submission:

1. Intake: The client provides the report source document in Word, Excel, PDF or InDesign, and the software converts it into XHTML.

2. Tagging: The document is tagged with the appropriate taxonomy concepts, supported by automation where appropriate.

3. Review: Tagging decisions are reviewed, usually by a second person, and issues are corrected.

4. Validation: The filing is tested against the XBRL specification, the relevant taxonomy and regulator-specific filing rules.

5. Filing: The completed report is submitted to the regulator or returned to the client for submission.

Late-stage changes usually create more pressure than the initial tagging. An audit committee may amend a figure in the final week, and every related tag and reference must be updated.

Keeping document preparation, tagging and validation on one platform makes those changes easier to control and helps keep the filing up to date through late revisions. Manual mapping becomes much harder to manage once several versions of the report are moving between the client, auditor and reporting team.

Building the Capability: People and Training

A firm does not need a large XBRL team to launch the service. A trained lead and reviewer can manage the first few clients, provided reporting deadlines do not all fall within the same period.

Much of the required knowledge already exists in the firm. Qualified accountants understand the underlying disclosures and financial statements, providing a strong foundation for selecting appropriate taxonomy concepts. They still need to learn the relevant taxonomies, filing rules and software workflows, but they are not starting from zero.

Platform training and certification can typically be completed within days, while practical expertise develops during the first live engagement. Firms should aim to schedule their first project before the busiest part of the filing season.

Capacity becomes increasingly important as the client base grows. ESEF and UKSEF deadlines cluster around the same period, meaning a firm may require substantial resources for a few months and considerably less for the rest of the year. The delivery model has to account for that seasonality from the start.

Choosing Your Delivery Model

The right delivery model depends on client volume, internal capacity and how much of the technical work the firm wants to deliver itself. Many firms use more than one model and adjust the balance as the service grows.

Many firms start with outsourced delivery to keep the first filing season manageable, then bring routine work in-house once client volume becomes more predictable.

The hybrid model often remains valuable even as the practice matures. Routine filings stay with the internal team, while complex extensions, difficult taxonomy decisions and peak-season overflow go to a specialist.

Whatever delivery model is chosen, the client will still hold the firm responsible for the quality and timeliness of the filing. Clear review procedures and defined responsibilities are essential whenever part of the work is outsourced.

Taking the Next Step: Becoming A CoreFiling Reporting Partner

CoreFiling offers several partnership models designed to support different delivery approaches. Most accounting firms join as Software Partners, combining CoreFiling’s solution with their own reporting, review, and advisory services.

Choose the Right Partnership Model

The software partner route does not lock firms into a single way of working. CoreFiling’s existing partners take different approaches:

• IRIS markets Seahorse under its OpeniXBRL brand to accountancy firms in the UK.

• BDO Portugal offers clients both direct access to the software and a fully managed iXBRL service.

• KFS Advisory supports listed companies across Germany and the wider DACH region with ESEF reporting.

• BRSANALYTICS provides Seahorse to clients in Malta and other international markets.

Prepare The Team For Its First Mandate

A firm does not need to launch across every XBRL reporting programme at once. Most start with the mandates their existing clients already face, such as ESEF or UKSEF, and build from there.

CoreFiling training can cover:

• XBRL and iXBRL Fundamentals: The concepts, terminology and structures behind digital reporting
• Product Training: How to create, tag, validate and review reports using Seahorse and Beacon
• Mandate-Specific Requirements: The taxonomy, report format and pre-submission checks for filing programmes such as ESEF
• Advanced Skills: Extension taxonomies, tagging quality and more technical XBRL workflows

Courses may be delivered using standard material or customised to the firm’s service model and target market.

Certification provides clients with confidence that a partner has invested in developing its XBRL capabilities. CoreFiling’s certified tagging partners are trained on Seahorse and follow established delivery practices. 

Launch The Service With CoreFiling’s Support

After training, the firm can shape the service around the needs of individual clients. Some may want a completed, filing-ready report, while another may prefer to licence Seahorse and ask the partner to review the final tagging.

CoreFiling supports partners through:

• Product training and onboarding

• Marketing and sales support

• Product support and updates

• Taxonomy and filing programme updates

Where appropriate, organisations approaching CoreFiling for reporting services may be introduced to certified reporting partners in their local market. Those partners provide the local market knowledge, reporting expertise and client support required for a successful engagement.

Give Clients a Service They Can Review and Trust

The partnership gives accounting firms several credentials they can use in client conversations:

• Filing-Specific Validation: Seahorse checks reports against the relevant technical standards, taxonomy and filing rules before submission. For UK corporate filings, Seahorse uses the same True North validation engine that Companies House uses to process incoming reports.
• Certified Software and Security: Seahorse holds XBRL International’s Report Creation Software certification, while CoreFiling holds ISO 27001 certification for information security; XBRL International develops and maintains the open XBRL standard that certification references.
• A Reviewable Tagging Process: Seahorse provides a review spreadsheet, commenting tools, and an audit trail of tagging decisions. Clients and reviewers can see how the report was tagged instead of receiving an unexplained final file.
• Experience Across The Standard: CoreFiling staff have authored or edited several XBRL specifications, including Inline XBRL, XBRL-JSON and XBRL-CSV.

Get in touch with CoreFiling to discuss which partnership model fits your clients, market and reporting services.