What is iXBRL? A guide for accountants

As digital technology continues to shape the way UK businesses operate, accountants face increasing pressure to keep their software, systems and processes up to date. Inline Extensible Business Reporting Language (iXBRL) has become one of the most significant elements of modern compliance, particularly for company tax returns and financial statements. This guide explains what iXBRL is, how it works and how accounting firms can use the right tools to manage it with confidence.

XBRL vs. iXBRL

Extensible business reporting language (XBRL) is an international standard for applying computer-readable tags to financial data. These tags turn traditional financial accounts into machine-readable data, enabling analysts, government agencies and software to review, compare and process information at speed. XBRL International maintains the global specifications, ensuring the same format and appropriate tag usage wherever the standard is adopted.

In the UK, the version used for financial reporting is Inline XBRL (iXBRL). iXBRL reports contain all the required computer-readable tags, but the tagging sits behind a familiar, human-readable front end. This means your clients’ financial statements look just like a standard document while still meeting HMRC and Companies House requirements.

iXBRL enables companies to file company tax returns online in a single document containing both the financial accounts and the supporting tax computation. Most companies now rely on iXBRL software to prepare accounts and computations in the correct iXBRL format.

When is iXBRL used?

Since 2011, most companies in the UK have been required to file company accounts and company tax returns in iXBRL format. This requirement came alongside the introduction of the joint filing service for HMRC and Companies House, allowing entities to file company tax returns and financial reports together.

Modern cloud-based systems – including Capium’s accounts and corporation tax tools – now automate this entire process. Accountants can create financial reports in HTML, apply the necessary computer-readable tags and file the final iXBRL file directly to HMRC and Companies House in one click.

What are the benefits of iXBRL?

iXBRL offers a wide range of practical advantages for accountants, businesses and their customers:

Faster and more accurate processing

iXBRL tagging allows computer systems to read and validate financial data automatically, speeding up the review and submission process for company tax returns. This removes the need for manual re-entry or cross-checking between multiple documents and ensures cleaner, more accurate submissions.

A consistent and compliant format

Using iXBRL ensures that financial statements, business data and computations are presented in the same format every time. This reduces risk, simplifies reviews and ensures your practice remains compliant with the latest HMRC and Companies House standards.

Better integration across systems

Inline extensible business reporting makes it easier to link different financial systems – from bookkeeping and payroll to tax and year-end accounts. With the right iXBRL solutions, practices can connect multiple data sources and create a single iXBRL report without additional handling or conversion processes.

Human-readable presentation

Even though iXBRL includes computer-readable tags, the front-end layout remains familiar and easy for clients to review. This allows accountants to share draft accounts for approval, safe in the knowledge that the embedded iXBRL data remains intact.

How does iXBRL impact accounting practices?

The impact of iXBRL varies depending on how your firm currently handles financial accounts and computations.

Manual accounts

Practices that still rely heavily on MS Word, Excel or manual bookkeeping may find the conversion process more time-consuming. HMRC does offer a basic tool for small companies, but it is limited and not suitable for more complex financial statements or business structures. Manual firms often need to outsource iXBRL conversion or introduce dedicated software to remain compliant.

Online accounts production

Firms already using cloud-based accounts production software will find the shift to iXBRL far easier. Modern systems automatically generate iXBRL accounts, tax computations and iXBRL files ready for submission. Reports remain fully readable, and clients can review them with no change in presentation.

Multiple-system workflows

Many firms still juggle several systems – spreadsheets, legacy tools and standalone databases. Converting these into machine-readable data can be difficult. Dedicated accounting software streamlines this by handling data from different sources, applying the appropriate tags and generating ready-to-file iXBRL accounts.

A note on responsibility

HMRC is clear that companies are responsible for ensuring their corporation tax return and financial statements are correctly tagged in iXBRL. In practice, most companies rely on their accountant. Using compliant software helps ensure the correct tagging, appropriate format and successful delivery to both HMRC and Companies House.

How do you convert to iXBRL?

If you’re planning to update your existing systems, many modern platforms offer easy iXBRL conversion and data import tools. Capium enables accountants to import data from a range of systems, generate iXBRL accounts instantly and manage all financial documents, statements and computations in one place.

By adopting integrated software, practices can:

• handle financial accounts for multiple client types
• generate iXBRL reports automatically
• eliminate manual conversion processes
• maintain consistent formatting and tagging
• offer faster turnaround times for customers

Moving forward

Compliance requirements evolve over time, and both HMRC and Companies House will continue updating their standards. Using cloud-based software ensures your practice remains future-proof, as new reports, tax updates and regulatory changes are added automatically. Instead of managing updates manually, accountants can focus on delivering accurate, efficient financial reporting for their clients.

If you’d like to learn more about Capium’s software and accounts production tools, contact our support team on 020 3322 5578 or visit our website to book a demo.