iXBRL Accounts Explained: What UK Companies Need to Know

iXBRL (Inline eXtensible Business Reporting Language) is the digital format required for filing company accounts with Companies House. If you run a UK limited company, your annual accounts must be submitted in this format.

Here is everything you need to know about iXBRL accounts and how they work.

What Is iXBRL?

iXBRL is a machine-readable format that combines human-readable HTML with embedded XML tags. This allows:

  • Humans to view the accounts as a normal document
  • Computers to extract and analyse the financial data automatically
The format was developed to standardise financial reporting globally and make it easier for regulators to process filings.

Why Does Companies House Require iXBRL?

Companies House requires iXBRL because it:

  1. Automates data processing - Financial figures can be extracted automatically without manual data entry
  2. Reduces errors - Tagged data is validated against defined rules
  3. Enables analysis - Regulators can analyse trends across all UK companies
  4. Meets international standards - Aligns with global financial reporting requirements
Since 2011, all company accounts filed online must use iXBRL format.

What Gets Tagged in iXBRL?

The key financial figures in your accounts are tagged with standardised labels. Common tagged items include:

Balance Sheet Items

  • Fixed assets (tangible, intangible)
  • Current assets (debtors, cash, stock)
  • Creditors (amounts falling due within/after one year)
  • Share capital and reserves
  • Net assets/liabilities

Profit and Loss Items

  • Turnover/revenue
  • Cost of sales
  • Gross profit
  • Administrative expenses
  • Operating profit
  • Profit/loss before and after tax

Company Information

  • Company name and registration number
  • Accounting period dates
  • Director names
  • Registered office address

iXBRL Taxonomies

Tags used in iXBRL come from approved taxonomies. UK companies typically use:

  • FRS 101/102 - For companies following UK accounting standards
  • UK-GAAP - General UK accounting taxonomy
  • EU-IFRS - For companies using international standards
The taxonomy ensures everyone uses the same labels for the same concepts, making data comparable.

How to Generate iXBRL Accounts

Option 1: Use Filing Software

The easiest approach is using software like TinyTax that generates iXBRL automatically. You enter your figures, and the software:

  1. Creates the accounts document
  2. Applies correct iXBRL tags
  3. Validates against taxonomy rules
  4. Submits directly to Companies House

Option 2: Use an Accountant

Accountants use professional software to prepare iXBRL accounts. They handle the technical aspects and ensure compliance with accounting standards.

Option 3: Manual Tagging (Not Recommended)

Technically possible but extremely complex. You would need to understand the taxonomy, create valid XML, and ensure all validation rules pass. This approach is impractical for most businesses.

iXBRL for Different Company Types

Micro-Entity Accounts

Micro-entities (turnover under £632,000) file simplified accounts with fewer tagged items:

  • Balance sheet only (no P&L required to file)
  • Limited notes
  • Fewer disclosure requirements

Small Company Accounts

Small companies (turnover under £10.2m) file abridged or full accounts:

  • Balance sheet required
  • P&L optional for filing (but must be prepared)
  • More detailed notes

Dormant Company Accounts

Dormant companies file minimal accounts:

  • Simple balance sheet
  • Usually just share capital and cash
  • Can be filed free with TinyTax

Common iXBRL Errors

Validation Failures

  • Missing required tags - Certain fields must always be tagged
  • Incorrect date formats - Dates must follow specific patterns
  • Calculation inconsistencies - Tagged totals must match component parts

Schema Errors

  • Invalid taxonomy references - Using tags that do not exist
  • Wrong data types - Text in numeric fields or vice versa
  • Namespace issues - Technical XML structure problems
Filing software handles these automatically, which is why using proper tools is recommended.

iXBRL and HMRC

HMRC also accepts iXBRL for corporation tax computations attached to CT600 returns. This uses a different taxonomy (CT taxonomy) but follows the same principles.

When you file with TinyTax, both the Companies House accounts and HMRC computations are generated in correct iXBRL format.

Do I Need to Understand iXBRL?

No. As a company director, you do not need to understand the technical details of iXBRL. You need to:

  1. Know your company's financial figures
  2. Use software that generates valid iXBRL
  3. Submit on time
The technical tagging is handled by your software or accountant.

Summary

iXBRL is the required format for filing company accounts with Companies House. It embeds machine-readable tags within human-readable documents.

Rather than worrying about the technical details, use filing software like TinyTax that generates valid iXBRL automatically. Enter your figures, and the software handles the rest.