iXBRL financial statements: which companies must file them

Most companies filing a corporation tax return must submit accounts in iXBRL unless they are small on all three tests: assets, turnover and employees.

iXBRL (inline eXtensible Business Reporting Language) is a format that tags each figure in a set of accounts so a computer can read it. It still displays as a normal document. Revenue requires many companies to submit their financial statements in iXBRL alongside the corporation tax return, Form CT1.

Who must file

• every company dealt with by Revenue's Large Corporates Division or High Wealth and Financial Services Division, for periods ending from 31 December 2012
• section 110 special purpose companies, for periods ending from 31 July 2013
• all other corporation tax filers, for periods ending from 31 December 2013, unless the exemption below applies

The small company exemption

A company outside those divisions doesn't need to file iXBRL if all three of these apply:

• total assets, before deducting liabilities, are less than €4.4 million
• turnover is less than €8.8 million
• the average number of employees is 50 or fewer

Failing any one of the three brings the company in. Companies and sole traders who don't have to file in iXBRL can do so voluntarily. Revenue's manual describes other situations where iXBRL isn't needed.

Timing

The iXBRL accounts are due with, or after, the CT1. A company's CT1 is due by the 23rd of the ninth month after its accounting period ends. So a December year end means 23 September of the next year. Revenue's manual sets out the time allowed for the iXBRL accounts where they follow the return.

What to include

• the financial statements prepared under company law, tagged using an accepted taxonomy
• certain mandatory tags, including turnover and gross profit (sales less direct costs), on the face of the detailed profit and loss account
• full accounts: abridged accounts filed with the Companies Registration Office are not accepted for this purpose

Accounting software and tagging services can produce the file; it is then uploaded through ROS. Getting the taxonomy right matters, because Revenue has warned against using taxonomies that don't fit the accounts.

Work it out

• Corporation tax for your company →

Sources

• Revenue: Corporation Tax payment and filing (CT1 and balance by the 23rd of month 9) (checked 25/10/2026)
• Revenue: Tax and Duty Manual Part 38-02-01J: Form CT1 2025 (ROS panels) (checked 16/10/2026)

General information, not tax advice. HeyPenny is not a tax agent.