In March 2026, HMRC published a consultation document seeking views on the following proposals: 

• Implementation of a standardised, fully tagged format for computations submitted as part of the company tax return. This is referred to as “full prescription”. As part of its enforcement approach, HMRC is considering blocking submissions that do not meet its software standards.
• Mandatory online filing for amended company tax returns. This would be subject to specific exceptions, including where HMRC’s corporation tax online service is unavailable at the point an amendment must be submitted and the statutory amendment window would otherwise expire. 

The proposals are explained in detail in an earlier article.

In its response to the consultation (ICAEW Representation 38/26), ICAEW’s Tax Faculty has recommended that HMRC: 

• extends the pilot phase for introducing standardised computation formats from one year to two years. This would allow HMRC to monitor the first round of submissions under the new standards for the first year and then give software providers the following 12 months to take any corrective action;
• ensures that the periodic revalidation of computation pages takes all changes into account (eg, changes in case law and HMRC guidance), and not just changes in legislation; 
• is more explicit about the safeguards it would put in place to minimise the impact on taxpayers and agents where tax software products are deactivated. At the very least, ICAEW would like to see any late filing penalties waived where they result from a blocked submission, unless for example the taxpayer or agent had already been notified that the relevant submission was likely to be blocked;
• allows taxpayers to file amended returns on paper that have passed the amendment deadline where the original return was submitted using estimated figures; and 
• reconsiders the proposed exception from mandatory online filing of amended company tax returns for HMRC service unavailability. ICAEW believes that the exception should be extended to cover any HMRC IT problems which prevent online filing of a return.  

ICAEW Representation 38/26 will be published on the 2026 tax representations page in due course.