UK and International Tax news
HMRC Consults On Corporation Tax Returns
Friday 20th March 2026
HMRC is seeking views on the implementation of full prescription of the content, format and XBRL data tagging of computations submitted as part of the company tax return.
Since late 2024, HMRC has worked closely with key software developers, the advisory community, professional bodies and other relevant stakeholders to design and deliver the first phase of prescribed requirements for Corporation Tax computations. This initial phase, encompassing accounts adjustments and capital allowances, was published in July 2025. The feedback from this initial phase has helped inform this consultation.
This consultation follows on from the early engagement to shape the prescription of computations requirements. This has included targeted discussions and technical workshops with software developers, professional bodies and tax advisers. Early collaboration has allowed HMRC to test draft prescribed sections, understand the operational impacts on software products, and refine the approach in response to stakeholder feedback. Developers also highlighted the need for realistic implementation timelines, which informed the decision to move to a formal public consultation. The early engagement has provided a strong foundation for the proposals now being consulted on.
The latest consultation invites further feedback on implementation timelines for the prescription of CT computations, arrangements to ensure a smooth transition from the current rules, and proposals for proportionate enforcement mechanisms to secure compliance.
The consultation also addresses mandatory online filing for amended company tax returns and invites feedback on potential issues. The requirement to file original company tax returns online has been mandatory for virtually all companies since 1 April 2011. However, amendments to returns may currently be submitted by written correspondence setting out the required changes.
While circa 95% of amendments are submitted online, HMRC continues to receive amendments in other formats. These submissions can lead to difficulties for HMRC and customers, including risk of errors due to manual processing, delays in processing claims or refunds due to the need for manual processing, and a lack of clarity whether a letter is an amendment or not.
Corporate Interest Restriction returns and those containing research and development claims must be submitted online. HMRC considers the standardisation of computations is the right time to fix the gap in the baseline requirement so that all amendments must be submitted electronically.
HMRC proposes that it will become mandatory to file amendments to company returns online. The consultation covers the exemptions which will apply and seeks views on whether other exemptions to mandatory online filing of amendments should be considered. It also asks whether, for practical reasons, mandation should commence later than 1 April 2027.
This consultation does not propose any changes to a company’s existing right to amend a return, nor does it propose altering the statutory time limits for amendments.
The consultation runs for 12 weeks starting on 10 March 2026 and ending on 2 June 2026.
The government will analyse and publish a response to the views expressed by stakeholders with an implementation timescale. The government will announce its preferred approach for enforcement at a later date.
If you would like more information on the above, please contact Keith Rushen on 0207 486 2378.
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