Working with HMRC on known issues related to MTD 2025/26

We are glad that so many untied users are in MTD early. We think that this gives a good experience, and hopefully helps you get used to MTD and untied.

The filing integration and systems are new for 2025/26 at HMRC as well. We are working closely with them to make sure that issues are identified and resolved.

A note from HMRC

"We are pleased that so many untied users have chosen to be in MTD early, and have been the first to file end of year MTD tax returns for 2025/26.

Making Tax Digital is a major step forward in how people file their taxes and has involved a decade of planning and transformation.

Much of this is new and involves complex systems and integrations at HMRC and in software.

As an early filer, you are a pioneer helping to make sure things are set up for the future. untied are able to identify live service issues to HMRC as a recognised developer and we work together to resolve them.

For those filing between April and July, special thanks. This is when we expect most issues to be identified and resolved.

For those who want to file later, a reminder that the deadline is 31 January 2027 though we encourage you to submit earlier. You can file amendments if something needs to be changed." Chris Jennings, MTD Software Lead, HMRC

Reassuring you about deadlines

The end of year return for 2025/26 is due by 31 January 2027. You do not need to file this before making your first quarterly update for 2026/27. See also this article on end of year filing.

Known issues

Users have reported the following issues with 2025/26 end of year filing and we have escalated where appropriate to HMRC as they may relate to data errors at their end.

Error	Description	untied comment
Cannot set accrual accounting for 2026/27		This is an HMRC system restriction. The accounting basis can currently only be set in HMRC systems after the end of a tax year. We and other parties have suggested a change to the flow which we are pleased that HMRC are considering.
Incorrect state pension figure (see also Cannot amend HMRC benefit eg for incorrect value for state pension error description below)		There is a known issue with incorrect state pension figures for the 2025/26 tax year if someone started their pension in that year. HMRC are working on a fix. If you have other issues re state pension then get in touch.
C55008	Period submission does not align to accounting period start date of 2025-04-06. Please amend and resubmit	Reported to HMRC. If this relates to self-employment you could try changing your business settings For most users this is now fixed - try again and if you still have issues let us know.
C55013	Period submissions do not align to accounting period end date of 2026-04-05. Please amend and resubmit	Reported to HMRC. If this relates to self-employment you could try changing your business settings For most users this is now fixed - try again and if you still have issues let us know.
C55107	One or more employments have no directorship declaration submitted. Please submit.	Users can fix this if it relates to a listed employment. We have updated the Employment section of our end of year filing article to explain what to do. Let us know if you still get this error We were also seeing this even if someone has no employments (or has pension income). We understand from HMRC this has now been fixed, but if you still have issues, contact us to escalate it further with HMRC.
C55326	Periods of Account information is required for all Self Employments. Please submit.	Users can fix this. Follow these instructions to change your business settings. Let us know if you still get this error
Internal server error		This is could be because you're signed up to MTD for 2026/27 but are trying to file for 2025/26. If you want to file for 2025/26, you will need to swap back to self-assessment and can then file from untied. If you're not sure contact us.
Matching resource not found		This could be for a number of reasons at HMRC - it's a general error message. Contact us and we can investigate.
HMRC Error: The client or agent is not authorised		This is generally because you are NOT yet properly signed up for MTD, but have linked the software. Note that signing up for MTD is different to authorising the software. Contact us if you want us to look into this for you
	No MTD obligations showing	This is a known issue which needs to be resolved at HMRC. Contact us if this applies to you.
	Cannot amend HMRC benefit eg for incorrect value for state pension	You may get an error that you can't amend an HMRC record. You may need to create your own state benefit pension record which includes the right value. When you do your calculation before submitting, check that the right total is included (rather than adding both).
	Tax year overview is blank - or incorrect amounts are showing as due in HMRC systems	Some of these are populated from HMRC's old systems, not from MTD. They may not show correct information - see also this article on seeing payments on account. If you have made an MTD filing that will mean you can reduce your second payment on account for 2025/26 (due by 31 July) then get in touch. This will typically apply if you have filed your end of year tax return via MTD and your total tax for 2025/26 is less than it was for 2024/25.

If you get further errors then let us know.