Edition 3: Making Tax Digital for Income Tax — software developer newsletter
Published 29 May 2026
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Welcome to the May edition of the Making Tax Digital for Income Tax — software developer newsletter, providing updates on service performance, API changes, and key information following mandation go live.
This edition highlights areas of focus as the service moves into live operation, including:
- API versioning actions
- recent updates to support testing and production readiness
- insights from live service issues to support ongoing stability
API Lifecycle
API status summary
To help you stay aligned with the latest MTD for Income Tax API changes, the table below provides an update on the status of the API versions.
| API | Version | Deprecation date | Retirement date | Required action |
|---|---|---|---|---|
| individuals-capital-gains-income-api | V2 | 16 April 2026 | within 6 months | Migrate to latest supported version |
| individuals-reliefs-api | V2 | 16 April 2026 | within 6 months | Migrate to latest supported version |
What this means
API versions are deprecated shortly after a new version is released and the deprecation period last 6 months. Existing subscribers can continue to use deprecated versions, but new subscriptions are not permitted.
After a deprecation period, APIs are retired and removed.
Several APIs are now progressing though the lifecycle. You must check and action the following:
- review the API versions your software uses
- migrate to the latest supported versions
- ensure you are not relying on deprecated APIs, as these will be removed
Recent API updates
Recent updates to MTD APIs are outlined below to support testing and readiness for production release.
Available in External Test (ET)
The following APIs are available from 24 March 2026 and are ready for testing:
- individual-losses-api (V7)
- individuals-partner-income-api (V1)
- individuals-tax-liability-adjustments-api (V1)
Live in production
The following APIs are available from 24 March 2026 and are now live in production:
- individuals-capital-gains-income-api (V3)
These updates are part of ongoing improvements to the MTD platform. Developers may wish to review the latest API documentation and prepare for adoption where relevant.
You can view upcoming API changes on the MTD for Income Tax API roadmap.
What’s next
Developers should take note of the following dates:
- quarter 1 submissions open: 1 July 2026
- quarter 1 deadline: 7 August 2026
- increased sign up volumes are expected through June to July
Live service issues
This section highlights:
- the most common issues reported by software developers in May
- guidance to help you resolve these issues quickly
- an understanding of where HMRC is already taking action
Core service impacts
| Theme | What’s being reported | What developers may wish to check |
|---|---|---|
| Client or agent errors | Client or agent is not authorised error message when interacting with MTD | Before reporting an issue, first check the client or agent is using the gov gateways credentials which have the MTD enrolment attached and the correct National Insurance number suffix has been entered into software |
| Obligations missing after Final Declaration | A small number of customers lose their current year obligations after submitting a final declaration, preventing quarterly submissions | Advise users to wait up to a week before raising with HMRC and avoid duplicate submissions or escalation too quickly |
| Repayment delays | Customers who submitted through Self Assessment instead of MTD are experiencing delays to repayments | Do not resubmit through software and reassure users that repayments will be processed without further action |
| Construction Industry Scheme (CIS) balancing charge incorrect | CIS credits are not always reflected, resulting in incorrect balancing charges in software or digital accounts | Be aware figures may be incorrect and avoid relying on CIS-adjusted balances until resolved |
| Quarterly obligation not marked ‘complete’ | Some customers have submitted successfully, but obligations remain open | Do not prompt re-submission and monitor before advising corrective action |
Issue volumes continue to reduce, with more incidents resolved than raised this week and ongoing corrective work improving customer records.
For the fastest resolution, continue to raise LSIs through your account manager using the makingtaxdigital-softwarevendors@hmrc.gov.uk , ensuring that you complete the LSI template with the details of the issue.
Other known behaviours and planned changes
| Theme | What’s being reported | What developers may wish to check |
|---|---|---|
| New repayments service limitation | Agents currently cannot request repayments through the new service (customers must do this themselves) | Ensure journeys direct agents appropriately. Guide users to complete repayment requests directly |
| Reporting type mismatch | Some users show as ‘standard’ instead of ‘calendar’ reporting in software, despite their selection | Allow approximately one week before raising issues. HMRC is correcting records progressively |
| Sign up blocked for SA200 filers | Customers who filed a short tax return (SA200) cannot sign up to MTD | Direct affected users to support to convert to SA100 and avoid repeated sign-up attempts |
| State pension pre-population inaccuracies | Incorrect state pension amounts may appear, impacting calculations | Use amend or create endpoints where needed. Expect fix in a future release |
| Business Source Adjustable Summary (BSAS) — Residential Financial Cost (RFC) | RFC incorrectly appears in BSAS despite no longer being an allowable expense | Prevent RFC adjustments in BSAS and inform users that values will still be handled correctly in quarterly updates |
Service updates
Read the latest planned downtime on the API platform status page.
Customer and agent guidance updates
What’s changed recently
Most of the MTD sections have been refreshed on Use Making Tax Digital for Income Tax - Send quarterly updates - Guidance - GOV.UK, including:
- clarification to support understanding of calendar vs standard update periods
- a new section has been introduced to cover making changes after the fourth quarterly update, helping users understand how to adjust their data before finalisation
Improvements have also been made within the Making Tax Digital: technical publications - GOV.UK to support clearer developer implementation.
What’s coming next
The final section of the MTD guide, ‘Submit your tax return’, will be updated shortly.
Ongoing work continues on:
- changes of circumstances
- exemptions guidance
Guidance planning for the year ahead is underway, with further updates due to be shared over the summer.
Exemptions update
Exemptions for customers claiming averaging relief (SA104) in 2024 to 2025 will not be applied automatically. Guidance is being updated to support users where appeals are rejected.
Guidance performance
Engagement with MTD guidance continues to remain strong, with usage and feedback increasing.
Engagement rates are consistently within the expected ranges, and user feedback is being actively reviewed to inform ongoing improvements.
Communications update
This section provides an update on recent communications activity related to Making Tax Digital for Income Tax.
MTD ready — recognised by HMRC trademark
The expiry date for use of the ‘MTD ready — recognised by HMRC’ trademark has been extended to 1 July 2027.
Software developers who are already approved to use the trademark can continue to use it as normal. An updated version of the ‘HMRC branding principles for software developers’ marketing and events’ document has been shared with approved vendors.
Developers who have not yet applied but wish to use the trademark can:
- complete the official request form
- submit the completed form to makingtaxdigital-softwarevendors@hmrc.gov.uk
Requests are typically processed within 3 to 5 working days.
Developer engagement and feedback
Views are welcome on how HMRC guidance could be used more effectively within software products. This could include:
- linking directly to relevant guidance
- surfacing content within products
- using HMRC’s digital assistant
- walking developers through existing guidance content
Ways to engage and provide feedback include:
- HMRC Developer Forum on the HMRC Developer Hub
- next monthly MTD Technical Delivery Forum — 7 July 2026
- Software Developer Feedback Survey — take a moment to complete the survey to help HMRC improve future newsletters