Working with HMRC on known issues related to MTD including end of year 2025/26 and first quarter 2026/27

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 at HMRC as well. We are working closely with them to make sure that issues are identified and resolved.

There are also issues relating to linking to HMRC and the first quarterly updates.

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." 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.

The first in-year quarterly update for 2026/27 is formally due by 7 August 2026. But if there is a technical issue then don't worry. HMRC have said there are no penalties associated with in-year updates for 2026/27. We are in daily contact with HMRC and are working with them on general and specific issues.

Known issues

Users have reported the following issues with 2025/26 end of year filing and 2026/27 setup. We have escalated where appropriate to HMRC.

Error	Description	untied comment
HMRC Error: Your HMRC connection is still being finalised. This can take a few minutes after connecting — please try again shortly.	Appears when linking the software	This is an untied holding message. Refresh - it may resolve or if you get another error see below.
404 No obligations found using this filter	This appears when you are looking at your MTD quarterly update obligations	This is a known issue with some taxpayers where HMRC need to reset their MTD obligations.
HMRC Error: The client or agent is not authorised	Appears when trying to link software to HMRC	This is generally because the taxpayer is not signed up to MTD - if you are an untied user contact us and we can do this for you. This can also be an issue with the Government Gateway account (or One Login) not being the one that is linked to the user's self assessment details. Generally you will still see the button to connect to HMRC to try again - if you don't get in touch and we can reset the connection. To find out if you're using the right account, our suggestion is to log directly into your personal tax account, and if you can see self assessment you're in the right place. If you are seeing self assessment all set up with the same account that you are linking to untied, then contact us. If you are not seeing self assessment, try to add it or try another Gateway login. You can also contact HMRC on 0300 200 3600 to find out which of your Gateway accounts to use (though users have reported that navigation is complicated). They may say it is a problem with the software, but try to persist as we have confirmed it is not at our end (they can't see the same logs we can!).
	National Insurance number mismatch errors	Try changing the last letter to another letter from A,B,C,D. The last letter historically related to payment timings. The rest of the national insurance number is still used by many systems as the key identifier. However in some aspects of MTD a full match is required - we have found that someone can go a whole career using a different final letter to those in HMRC systems.
	Incorrect payments due - including for payments on account. This can include suggesting that no tax is due.	We have seen multiple issues: Note that if you are in MTD, then what you owe HMRC may appear in two places in their systems We also hear that submissions may not fully be reflected in HMRC systems - we think that this relates to the transfer of records from HMRC's old system to the new one If in doubt, we suggest to take a screenshot of what you are relying on in terms of the amount that is due
	Various calendar election issues	There are three things here: A calendar election needs to be made before the first quarterly update is submitted in a year The first calendar election period is likely to be 6 April - 30 June - this is usual behaviour. We suggest that as part of the year end process, there is a check that all income and expenses for the 1-5 April period have been taxed/claimed once (note that in untied transactions are displayed by tax year even if they are reported in a different year) We have also seen a mismatch in dates between what appears in HMRC systems directly, and what you will see in the software - we are trying to understand with HMRC why this is the case
	Multiple businesses all with the same name	This is an HMRC data limitation. If you have multiple activities, they may all appear with the same name in HMRC systems. We don't know which is which. You may be able to see this by logging into HMRC systems or by contacting HMRC.
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.