Consultation outcome

Modernising and standardising company tax returns — summary of responses

Updated 28 October 2026

1. Overview of responses

Background

As announced at Budget 2025, HMRC is introducing a prescribed format for the content and XBRL tagging of Corporation Tax computations. This work looks to address longstanding inconsistencies in the quality, consistency and usability of company tax return data.

Building on prior engagement, on 10 March 2026 the government published the consultation Modernising and standardising company tax returns. The consultation sought views on proposed implementation timescales and enforcement mechanisms for prescribed computations and potential issues arising from the requirement for amendments to Company Tax Returns to be submitted digitally.

The government is grateful to all who responded to this consultation. HMRC received 40 responses distributed evenly between representative bodies, advisory firms, software and technology providers, and businesses.

Alongside formal written responses, HMRC officials also met extensively with stakeholders throughout the consultation period where feedback was given on the consultation and the broader project.

Consultation responses

Respondents broadly supported the objective of greater consistency and standardisation and recognised the benefits of improving data quality to support HMRC’s compliance and customer service functions.

Respondents considered the proposed timelines challenging, citing the scale and complexity of the changes, the need for further co‑creation and testing and the importance of understanding and minimising any additional burdens placed on taxpayers, agents and software providers. More detail is provided in Chapter 3.

On enforcement, while respondents generally supported the need for software standards and proportionate measures to address non-compliance, they emphasised the importance of clear governance, transparent processes, effective communication and safeguards to protect taxpayers from unintended consequences of non-compliant software. Chapter 4 provides further detail on these responses.

While respondents broadly supported the mandatory online filing of amended company tax returns, many stressed the need for retaining appropriate exceptions and alternative filing routes where online submission may not be suitable, particularly for complex and historic cases. Chapter 5 provides further detail.

Wider feedback on the project

Many respondents were concerned that HMRC had not clearly explained the project’s objectives or consistently identified where new information requirements were being proposed. They noted that this made engagement and constructive challenge difficult.

HMRC acknowledges these concerns and the need for greater clarity to support effective engagement and has revised its approach to stakeholder meetings accordingly. Chapter 2 sets out the rationale for prescribing and standardising Corporation Tax computations, the proposed approach and how stakeholders can contribute.

Several respondents raised concerns about how prescribed computation requirements would affect the Corporation Tax software market. They noted that software products are often designed for particular customer groups and may not need to support every element of the prescribed computation. Requiring all products to accommodate the full range of prescribed requirements, regardless of its intended user base, could increase development and maintenance costs and create unnecessary complexity for users.

Further linked work on the future administration of Corporation Tax

The government recognises that many of the responses to this consultation extend beyond prescribed computations and the digital filing of amended returns and raise wider questions about the future administration of Corporation Tax. Alongside this work, the government is seeking views through the Call for Evidence on Modernising the Administration of Corporation Tax, which explores the longer-term future of Corporation Tax administration. This includes the role of technology, software, data, automation, information flows and proportionate administration across different parts of the Corporation Tax population.

Together, these strands of work will help shape a future Corporation Tax system that is easier to comply with, better integrated with modern business processes, supports businesses to get things right first time and enables more effective administration. The new Call for Evidence provides stakeholders with an opportunity to contribute to these broader strategic questions, and the evidence gathered through both exercises will help ensure that immediate reforms and longer-term modernisation are developed in a coherent and joined-up way.

The government recognises these concerns. Although the requirements are intended to improve consistency and data quality, software products will not need to present or support every element in all circumstances. The government will prescribe a comprehensive computation but software providers will only be required to include the sections that are relevant to their customer base in their products. As the requirements are developed further, HMRC will continue to work with software providers to ensure that the approach remains proportionate and reflects the differing needs of taxpayers, sectors and products.

2. Project objectives

Corporation Tax computations are a core component of the company tax return, providing the link between a company’s statutory accounts and its final Corporation Tax liability reported on the CT600 form. XBRL tagging enables return data to be processed automatically by software and has been mandatory for returns delivered on or after 1 April 2011. XBRL will remain a key part of the filing system for company tax returns submitted to HMRC and accounts filed with Companies House.

However, computations remain largely free format, so the presentation, structure and level of detail can vary significantly between taxpayers and software products. 

In many cases multiple XBRL tags have no obvious distinction between them, allowing for the same information to be tagged in different ways.  Examples include tags such as: “OtherOperatingExpensesFormat1 currentPeriod’ or “OtherOperatingExpensesFormat2 currentPeriod”, and “DepreciationAmortisationExpense currentPeriod” or “DepreciationAmortisationImpairmentExpense currentPeriod” which may be interpreted inconsistently due to the limited distinction between them. The project aims to simplify and standardise the use of tags by establishing a consistent approach to their application.

Similarly, software providers may use different labels for the same computation entry and its underlying tag leaving it a matter of interpretation for the taxpayer what each field covers. Where that interpretation differs from what was intended, an HMRC officer reading the computation, or machine reading the tag, may understand the entry differently to the taxpayer.

For example, the tags ‘Patent Box Adjustment’ and ‘Patent Box Adjustment 2016’ are both used in practice, regardless of whether the adjustment relates to the post-2016 Patent Box regime. In some cases, the same amount may even be tagged twice, using both tags.

The project aims to simplify and standardise the use of tags by establishing a consistent approach to their application.

Beyond tagging issues, inconsistencies in the format and level of detail of computations make it harder for HMRC to interpret, compare and process returns efficiently. HMRC continues to receive computations that do not clearly show how the tax liability was calculated, do not readily reconcile to the accounts or present key information in a way that supports interpretation or comparison. Legislation already specifies the layout and sequence of certain elements, particularly the core calculation, and software that departs from these requirements may produce incorrect results.

Errors can occur when taxpayers misinterpret what to enter in a particular box or where calculations are presented in the wrong sequence. This may result in taxpayers overpaying tax or underpaying and potentially facing penalties at a later date. HMRC routinely opens enquiries where information has been presented incorrectly or further clarification is needed to establish the basic facts of a return. This creates unnecessary costs and administrative burdens for both taxpayers and HMRC. The variability also limits HMRC’s ability to use data more effectively for risk assessment, customer service and wider modernisation of the Corporation Tax system.

This project aims to introduce a more consistent and structured approach to Corporation Tax computations. Standardising the entries and their tags will improve data quality, help users make the correct entries, increase assurance in the information HMRC receives, support compliance activity and customer service and reduce unnecessary contact.

3. Implementation timelines

This section summarises responses to consultation questions 1 to 4 of the consultation on the feasibility of the proposed timetable for implementing prescribed Corporation Tax computations. The timetable comprised four stages:

• collaborative development and refinement of draft specifications from April to September 2026
• publication of the final full prescription by the end of September 2026
• a build and test period from October 2026 to September 2027
• a live pilot period from October 2027 to September 2028

Question 1: Is the proposed 6-month collaborative development phase sufficient to refine the prescribed computation requirements?

Although a small number of respondents were comfortable with these proposed timescales, most did not consider the six-month collaborative development phase sufficient to refine the prescribed computation requirements.

Those holding this view consistently highlighted the scale, complexity and volume of the work required; including reflecting on the time taken so far as an indicator of likely further time needed. Concerns were raised over having time to properly consider:

• more views from taxpayers and in-house tax teams
• more complex sections (such as loan relationships)
• sector specific sections (such as insurance)
• overlap with broader information requirements on corporates

Several respondents also highlighted the need to check and engage on the whole computation once the individual sections are settled, to remove repetition and consider overall coherence.

Respondents who proposed an alternative timetable recommended extending the collaborative development phase by at least three months.

Question 2: Will the proposed approach of a limited roundtable participation provide effective coverage?

Several respondents considered that the proposed approach could give disproportionate weight to the views of larger organisations, software providers and advisers, while overlooking taxpayers’ role in the process, including those preparing their own returns. They cautioned that requirements may appear workable in theory but prove difficult to apply in practice and stressed the need to ensure that due consideration is given to what is proportionate for each business to provide.

Respondents suggested that participation should be broadened to reflect the diversity of the Corporation Tax population and recommended including:

• a range from smaller entities to large corporates
• specific sectors with unusual tax requirements such as the charity and insurance sectors

Respondents also recommended establishing a formal mechanism for stakeholders not involved in the roundtables to review the outputs and provide feedback. Some respondents suggested that this should include a direct route for raising concerns with HMRC where necessary.

Question 3: Do you agree that 12 months from receipt of full prescription requirements is enough time to deliver finalised products? If not, explain your reasoning.

Respondents highlighted consistently that any agreed timescale needed to be flexible and responsive to delays in finalising requirements or significant issues emerging during development. Respondents noted that meaningful development cannot begin until the final prescribed requirements are clear, consistent and fully tested.

A small number of respondents considered a 12-month period sufficient to deliver final products provided the final specifications are clear, complete and stable. These respondents were confident in the adaptability and existing readiness of their software.

But most respondents did not consider a 12-month implementation period sufficient and instead recommended an implementation period between 18 to 24 months from publication of the final specifications. These respondents indicated that substantial redevelopment of existing software would be needed, including changes to presentation layers and underlying data structures across a wide range of computation sections. These issues were seen as particularly acute for smaller software providers.

Many software developers commented that they face competing demands from HMRC and broader government, including legislative and Budget changes, recommending that HMRC ensure the timing reflects on those broader demands.

Question 4: Is a 12-month pilot phase sufficient to identify and resolve implementation issues?

While respondents expressed a range of views, most did not consider a 12‑month pilot phase sufficient to identify and resolve implementation issues before mandation. A minority agreed that a 12-month period could be adequate, where processes and systems are stable, some noting this would depend on the timing of the start of the pilot period and the readiness of software and users.

A common concern was that a single year would not be sufficient to ensure all parts of the return are working correctly, particularly for more complex areas of the return and that more than one filing cycle would be required to identify and resolve issues as they arise. Differences in accounting periods and filing deadlines could mean that some businesses have only limited experience of the new requirements during the pilot period.

Several respondents were unclear on how the pilot would operate in practice, including whether it would function as a testing phase or effectively become mandatory from the outset. Others commented that, if all returns must comply with the new format during the pilot, it would limit developers’ opportunities for iteration, testing and refinement.

A number of respondents favoured a longer pilot period, with suggestions ranging between 18 months and 24 months, to allow initial submissions to be monitored, issues to be identified and addressed and software providers and users to make necessary changes before a further period of testing under more stable conditions.

Respondents also emphasised the importance of a phased or staged approach including voluntary early adoption, incremental rollout across different user groups and clear transitional arrangements between development, testing and full implementation.

In addition, respondents highlighted the need for greater clarity on how the pilot would interact with accounting periods, amended returns and the overall implementation timetable.

Additional comments on the implementation timeline

Some respondents raised broader points about the practical implications of implementing prescribed Corporation Tax computations. While not linked to specific consultation questions, these comments provide further insight into the scale of the change involved, the potential impact on taxpayers, agents and software providers and the importance of ensuring that the final requirements are proportionate, practical and clearly justified.

Respondents emphasised that implementation extends beyond software development; requiring extensive testing using real-world scenarios. They emphasised the need for sufficient time to train end users, enable feedback to developers and test that the software works effectively with existing systems and processes. Respondents also noted Corporation Tax computations are often finalised at year end following professional review meaning that implementation plans must reflect existing compliance and reporting practices.

Several responses noted that the volume of required data and level of detail proposed appear greater than current requirements, which increases both the complexity of the return, the compliance burden and in some cases costs. Respondents also raised concerns that some elements may appear to request information beyond that realistically required to determine the tax liability and that HMRC should therefore take additional time to review whether all the prescribed information is realistically required.

Government response

The government is grateful for the detailed feedback provided by respondents on the proposed implementation approach and timetable. The responses highlighted the scale and complexity of the changes required, the need for further refinement of the prescribed computation requirements and the importance of ensuring that implementation is proportionate and deliverable for businesses, agents and software providers.

In response to this feedback, HMRC paused the co-creation process over the summer period and did not proceed with publication of a final full prescription in September 2026. During the pause, HMRC reviewed the feedback (including through discussions with stakeholders) and reconsidered proposals for additional information to ensure that the next phase of development has is informed by the practical and operational concerns raised.

The government recognises that prescribed Corporation Tax computations may create additional costs and burdens for businesses, agents and software providers, particularly where changes are required to existing systems, processes, client engagement or products must be adapted. HMRC will continue to assess these impacts as the requirements are developed and will work with stakeholders to limit additional burdens as far as possible by ensuring that information requirements are proportionate, justified and clearly communicated.

Co-creation has now resumed, but on a longer and more flexible timetable. Rather than working to a fixed publication date, HMRC will take a more iterative approach, allowing sufficient time for further engagement, testing and refinement before requirements are finalised. This will include continued engagement with software providers, agents, representative bodies and businesses to ensure that the prescribed format is workable across the Corporation Tax population.

Implementation timescales will flow from this revised co-creation process. HMRC will not set final implementation dates until the requirements are sufficiently developed and stakeholders have had appropriate opportunity to fully consider their practical implications. Any future timetable will build in time for software development and testing, as well as time for agents and businesses to understand the changes, update processes and advise clients where changes may be needed.

4. Enforcement

This section summarises responses to questions 5 to 14 of the consultation which sought views on a proposed compliance and enforcement framework for Corporation Tax software. The consultation set out a range of options intended to support consistent software standards and ensure that returns are submitted using products that meet the prescribed requirements. These included publishing an Approved Corporation Tax Software Product List, validating updates to prescribed sections of software, using unique product identifiers, blocking submissions made through non-compliant software, introducing a graduated process for addressing non-compliance and considering monetary penalties for deliberate or repeated non-compliance by software providers. The consultation also sought views on locking XBRL tags within software products, including the potential need for safeguards or limited override functionality where appropriate.

Question 5: Do you foresee any issues, risks, or unintended consequences from publishing an Approved Corporation Tax Software Product List?

Respondents recognised the potential benefits of an approved software lists, but some concerns were raised on the effect it would have on market competition, particularly for smaller providers and businesses using bespoke software. They emphasised the need for HMRC to publish clear approval criteria, to carefully communicate what “approved” means and to make arrangements to protect taxpayers if a product loses approved status.

Question 6: Do you see any practical challenges in validating only the prescribed sections of software that have been updated, rather than re-validating the entire product? Please explain and, where possible, provide examples.

Most respondents were receptive to validating only the section of the software that had changed but noted that computations are interconnected and changes in one area may affect the wider product. They favoured a proportionate approach which combined the targeted validation with a wider testing where necessary alongside a timely and clear HMRC process.

Question 7: Do you have any concerns about the proposal to block submissions that do not meet the software standard?

Most respondents opposed blocking submissions where this could prevent taxpayers from meeting their filing obligations because of software issues outside their control. They considered blocking appropriate only as a last resort, with clear standards, sufficient notice, transitional arrangements and protection for affected taxpayers.

Question 8: Do you have any comments on the proposed approach of a unique identifier for each product, including any operational or security considerations we should take into account?

Respondents were broadly supportive of unique software identifiers but sought clarity on how they would apply across products, versions and modules. They also emphasised the need for secure and efficient processes for issuing, updating, revoking and restoring identifiers without unnecessarily disrupting users.

Question 9: If bridging software is used, would users need to be informed in advance of key revocation?

Respondents agreed that users should be notified in advance where revocation could affect their ability to file, particularly where bridging software is involved. Notifications would need to be clear and timely, allowing users sufficient opportunity to make alternative arrangements and meet their filing obligations.

Question 10: Do you have any comments on the proposed multi-step process (review, warning, temporary removal from the whitelist, gateway rejection and possible publication on a block list) appropriate to address non-compliance?

Respondents broadly supported a graduated approach focused initially on engagement and remediation opportunities, with stronger action reserved for serious or persistent non-compliance. They asked for clear decision-making criteria, timely notification and safeguards for users, alongside an appropriate process for providers to challenge or seek review of decisions.

Question 11: Do you have any concerns with the proposal to introduce monetary penalties as a sanction for deliberate or repeated non-compliance by software providers?

Views on monetary penalties were mixed, although respondents generally considered that penalties should be reserved for clear, deliberate or persistent non-compliance rather than genuine errors or differences in interpretation. They also stressed the need for proportionality, transparent criteria and appropriate review or appeal processes.

Question 12: Do you agree with the proposal to lock tags in software products to prevent users from altering them? Are there circumstances in which users should be permitted to edit or override locked tags? If so, what safeguards should be in place?

Question 13: What potential technical or operational challenges might arise from implementing locked tags in tax computation software?

Question 14: Could locking tags adversely affect usability or the flexibility required for accessibility adjustments? Please elaborate.

Respondents broadly supported greater control over XBRL tags to improve consistency and reduce errors, noting that unrestricted changes could undermine the objective of standardised Corporation Tax data.

However, some considered that a fully locked approach could prevent complex, unusual or sector-specific tax positions from being represented accurately. They supported limited alternatives or overrides where necessary, subject to justification, an audit trail and appropriate access controls.

Respondents also emphasised the need to maintain tagging requirements as tax rules change, manage interactions across the computation and ensure that any approach is fully tested for accessibility.

Government response

The government recognises respondents’ concerns about the potential impact of enforcement measures on taxpayers, agents and software providers. Respondents stressed the need for clear processes for dealing with non-compliant software, effective communication with affected users and appropriate safeguards to ensure taxpayers are not disadvantaged by issues outside their control.

The government also acknowledges the need for flexibility within the prescribed computation requirements. The approach must improve consistency and data quality while allowing complex, unusual or sector- specific positions to be represented accurately.

HMRC recognises that taxpayers, agents and software providers should be informed promptly and automatically when software fails to meet the required standard. This would require more integrated systems and processes to identify failures, notify affected parties and support appropriate action.

Respondents supported proportionate enforcement arrangements. The government agrees that any future approach should support compliance and software quality without placing unnecessary burdens on taxpayers, agents or software providers. HMRC will continue to engage with stakeholders as the prescribed requirements and wider implementation approach are developed further.

Given these factors, the government does not intend to take immediate action to introduce enforcement measures applying directly to Corporation Tax software providers. HMRC will revisit the position alongside its broader work on software standards.

5. Mandatory online filing of amended returns

Original company tax returns are already required to be filed electronically, but amendments to a return can currently be made in other forms (such as via email or post). The consultation sought views on introducing mandatory online filing for amendments to company tax returns. This included consideration of whether any exemptions may be required, the impact on different customer groups, and the proposed implementation date of 1 April 2027.

This section summarises responses to questions 15 to 17.

Question 15: Are there any types of amendment that should be excluded from mandatory online filing?

Overall, respondents generally supported the move towards digital amendments but emphasised the importance of targeted exemptions and transitional arrangements. These were seen as necessary to ensure that amendments can be made without imposing disproportionate burdens on taxpayers or agents.

A minority of respondents said that there should be no exclusions. However, the majority raised the need to retain flexibility for complex or non-standard amendments. Specific circumstances raised were amendments:

• made in connection with enquiries and litigation
• for complex changes, including amendments across multiple companies or periods
• where detailed narrative and supporting information are needed
• for historic returns and where transitioning between software

Respondents also referred to HMRC systems limitations, including file size restrictions, limits on the number of amendments, challenges in processing complex periods of account and wider IT issues that could prevent online filing in practice.

Respondents also noted that a lead-in time would be required by taxpayers currently unable to file amendments electronically for changes to software and internal processes and data migration.

Question 16: Are there particular customer groups likely to be disproportionately affected by the mandatory online filing of amended returns?

Reflecting similar issues highlighted for Question 15 on exclusions, several respondents noted that those with complex situations, enquiries and litigation or transitioning between software would be more challenging.

Some respondents also felt that smaller businesses and unrepresented taxpayers may face greater challenges due to having simpler software, less structured record keeping and limited digital capability.

Question 17: Do you agree that mandatory online filing for amendments from 1 April 2027 is reasonable?

Most respondents agreed 1 April 2027 would be an appropriate commencement date provided that the following matters are addressed sufficiently in advance:

• HMRC systems are tested to support amendments (see Question 15)
• sufficient guidance and support is provided to taxpayers and agents
• appropriate exceptions, including any necessary transitional arrangements, are put in place

Respondents emphasised that guidance should cover:

• whether the commencement date would apply to submissions made on or after that date, or to accounting periods beginning or ending on or after it
• how long periods of account and amendments to earlier returns would be treated

Government response

The government welcomes respondents’ broad support for making online filing the default method for submitting amendments to company tax returns. Digital filing supports more efficient processing, improves data quality and helps ensure that amendments are handled consistently. 

The government recognises the concerns raised about particular cases and technical constraints. It remains committed to increasing digital filing where this is effective and appropriate, while ensuring that taxpayers and agents retain a workable route to amend returns accurately in cases where online filing is unsuitable.

The government will therefore proceed with the move towards mandatory online filing for amended returns, with targeted exceptions and fallback routes where necessary. These will cover amendments:

• made in connection with enquiries or litigation
• involving complex changes, including amendments spanning multiple companies or accounting periods
• to returns originally filed using software which is no longer available to the submitter
• where HMRC systems or other technical limitations prevent online filing

Existing exemptions from online filing for original returns will continue to apply to amendments.

To allow time to define these exceptions and provide supporting guidance, mandatory online filing for amendments will apply to amendments submitted on or after 1 April 2028.

Before implementation, HMRC will publish further guidance, including full details of the exceptions and fallback routes described above. HMRC will also continue to work with software providers, agents and representative bodies to ensure that the approach is practical, proportionate and supported by appropriate transitional arrangements.

Amendments to returns for periods before the introduction of prescribed computations will not be required to comply with prescribed requirements introduced subsequently.

6. Next steps

Prescribed Computations

As noted above, following stakeholder feedback, HMRC paused the co-creation sessions in June 2026. The process will follow a longer, more flexible timetable, allowing additional time to review, refine and test the draft prescribed requirements before they are finalised.

HMRC will continue to engage with software developers, agents, representative bodies and businesses, while seeking broader participation from across the Corporation Tax population. Engagement will focus particularly on sectors and taxpayers with complex or specialist requirements, helping to ensure the prescribed format accommodates a wide range of commercial and tax arrangements. HMRC is committed to continual assessment of the potential impacts and burdens associated with the proposed requirements and will identify and implement opportunities for simplification where appropriate.

The government will consult on the completed set of prescribed requirements in early 2027. This will give stakeholders across the board the opportunity to review the full prescription, assess any operational or compliance impacts and identify any remaining issues. As part of this work, HMRC will also review the information currently provided through the CT600 supplementary pages and consider whether the prescribed computation could remove the need to provide it separately. Consultation feedback will inform the subsequent timeline for software implementation. The government will communicate the timetable clearly once it has been confirmed.

The consultation highlighted the importance of clear governance, proportionate safeguards and effective communication with taxpayers, agents and software providers in relation to enforcement of the prescribed requirements. The government does not intend to take immediate action to introduce enforcement measures applying directly to Corporation Tax software providers and will revisit the position alongside HMRC’s broader work on software standards.

Amended Returns

The government remains committed to making online filing the standard method for submitting amended company tax returns. In reaching this decision, it has considered respondents’ concerns about complex amendments, historical returns, technical constraints and transitional issues.

Online filing of amended company tax returns will, therefore, be mandatory from 1 April 2028. Subject to any exclusions or exceptions set out in guidance, the requirement will apply to amendments submitted on or after that date, regardless of the accounting period to which they relate.

HMRC will publish detailed guidance before commencement. This will explain how the requirement applies to historic returns, long periods of account, returns originally submitted using legacy software and circumstances where alternative filing routes remain available.

A limited number of exceptions will be retained where an alternative filing method is necessary for an amendment to be submitted effectively. Non-digital filing will also remain available where an HMRC systems issue prevents online submission by the statutory deadline.

Annex A: List of stakeholders consulted

ACCA (The Association of Chartered Certified Accountants)

Acorah Software Products Limited (TaxCalc)

Aegon UK

Asda Stores Ltd

Association of British Insurers

Association of Taxation Technicians

BASDA (Business Application Software Developers Association)

BDO

Beeston-Clarke Accountants Ltd

BUFDG

Canary Wharf Group

Confederation of British Industry (CBI)

Deloitte LLP

eh7 Internet Ltd

Events Management

FreeAgent Central Limited

Grant Thornton UK Advisory & Tax LLP

Green Pike Ltd

ICAEW

Irish Taxation Software Services Limited

Isogon Systems Limited

MACE Systems Ltd

Moore Kingston Smith

Naiyas Technologies and Services Ltd

PwC LLP

RSM

Sage

Silph Co. Limited

Tax Systems

TaxInfo Hub

Thames Williams Limited

The Chartered Institute of Taxation

The Institute of Chartered Accountants of Scotland (ICAS)

Thomson Reuters

UK Finance

Wilson Partners Limited

Xero

Two individuals