HMRC’s Agent Update 143 landed in May 2026, and it’s dense. Between backdated mileage rate changes, a new R&D assurance pilot, imminent consultation deadlines, and live penalty regimes, there’s enough in here to catch out any finance team that isn’t paying attention. Here’s what matters — distilled into six actions you need to take before the summer.
1. Re-Run Payroll for the New 55p Mileage Rate
The Approved Mileage Allowance Payment (AMAP) rate has jumped from 45p to 55p per mile for the first 10,000 business miles — the first increase in over a decade, triggered by the government’s Iran crisis support package. Critically, this is backdated to 6 April 2026.
If you have a mobile workforce — field engineers, consultants, regional managers — and you’ve been processing mileage claims for April and May 2026 at the old 45p rate, you’ve been over-deducting NIC and income tax on the difference. That needs correcting now.
Action: Instruct your payroll team to re-run April and May 2026 calculations using the new 55p rate. Any employees reimbursed above the old rate who had NIC/IT deducted on the excess need refunds processed. HMRC is updating job expenses claim forms, but don’t wait — the liability sits with you. For detailed guidance on vehicle mileage tax relief, see HMRC’s vehicles for work guidance and the Business Income Manual at BIM75005.
Self-employed individuals should note the new rates apply to 2026-27 Self Assessment returns.
2. Consider the R&D Advance Assurance Pilot — Before It Fills Up
Launched on 18 May 2026 and running for 12 months, HMRC’s new R&D Advance Assurance Pilot is a genuine opportunity for SMEs to de-risk their R&D tax relief claims before submission.
The pilot is free and voluntary. It covers up to two areas per project from the following:
- Whether the project qualifies as R&D
- Overseas expenditure eligibility
- Contracted-out R&D treatment
- PAYE/NIC cap exemption applicability
HMRC is targeting a 40-day response time. This cannot be combined with full claim advance assurance, so it’s one or the other.
Action: If your portfolio companies are claiming R&D relief — particularly where overseas subcontractors or contracted-out arrangements create ambiguity — apply now. A 40-day turnaround means you could have certainty before your next board pack. Given HMRC’s aggressive posture on R&D compliance over the past two years, getting written assurance on borderline areas is worth the administrative effort.
3. Reassess EOT Exit Structures After the CGT Relief Cut
This one has been in effect since 26 November 2025 but continues to catch people out. CGT relief on qualifying disposals to Employee Ownership Trust trustees has been cut from 100% to 50%. The remaining 50% is held over and crystallises on a future trustee disposal.
For PE-backed businesses considering EOT structures as part of exit planning, this fundamentally changes the economics. What was once a fully tax-free exit for founders is now a partially deferred tax event. The held-over gain doesn’t disappear — it attaches to the trust and surfaces later.
Action: Review any live or planned EOT transactions in your portfolio. Model the after-tax proceeds under the new 50% relief regime and compare against alternative exit routes. If you’re advising founder-managers on succession, the conversation has changed materially. See HMRC Helpsheet HS277 for the updated mechanics.
4. Respond to the CT Amended Returns Consultation — Deadline 2 June 2026
HMRC’s consultation on mandatory online filing of amended Company Tax Returns proposes making online submission compulsory from 1 April 2027. The stated aim is to improve accuracy, speed up processing, and accelerate repayments.
The consultation closes on 2 June 2026 — that’s tomorrow. If you haven’t responded, you’re out of time, but the operational implications demand attention regardless.
Action: Even if you miss the consultation window, start planning for mandatory online amended CT returns from April 2027. Audit your current amendment workflow. If any of your entities still file paper amendments (and some do, particularly older entities with complex histories), you need a migration plan. Exemptions are proposed but not yet confirmed — don’t assume you’ll qualify. Groups with high amendment volumes should engage with HMRC directly or through their professional bodies.
5. File CIS Monthly Returns — Penalties Are Live
From April 2026, the Construction Industry Scheme penalty regime is fully operational. CIS contractors must file monthly returns, including nil returns. This is not optional, and the penalty structure is steep:
- Immediate: £100 penalty for late filing
- 2 months late: £200 additional penalty
- 6 months late: £300 or 5% of the liability (whichever is greater)
- 12 months late: Further geared penalty
The June 2026 filing deadline covers the April–May period. If your portfolio includes construction, property development, or infrastructure businesses, this is a live compliance risk right now.
Action: Confirm all CIS-registered entities in your group have filed for April and May 2026, including nil returns where no subcontractor payments were made. If a business has genuinely ceased CIS activity, submit an inactivity request (available in six-month blocks) to avoid the nil return obligation. Do not assume that “no activity” means “no filing requirement” — that assumption now costs a minimum of £100 per month.
6. Prepare for MTD for Income Tax — First Quarterly Deadline 7 August 2026
Making Tax Digital for Income Tax is live. Individuals with gross income exceeding £50,000 from self-employment or property (based on their 2024-25 return) must be signed up. The first quarterly update is due 7 August 2026.
This affects partners in partnerships, property investors, and sole traders — including those within PE portfolio structures where individuals hold property or trading interests personally.
Action: Identify all affected individuals across your portfolio. Ensure they have signed up for MTD for Income Tax, authorised an agent (if applicable), and connected MTD-compatible software to HMRC. The 7 August deadline is less than ten weeks away. If you haven’t started the software selection and onboarding process, you’re already behind.
Other Items Worth Noting
Agent Update 143 also covers several measures from the Iran crisis support package that affect operating costs:
- Fuel Duty: The 5p per litre cut has been extended to 31 December 2026, providing continued relief for logistics-heavy businesses.
- Red Diesel: Reduced from 10.18p to 6.48p per litre from 15 June 2026 — relevant for agriculture, construction plant, and certain industrial operations.
- HGV Vehicle Excise Duty: £1 renewal for the next 12 months, a material saving for fleet operators.
For businesses with international elements, HMRC’s AEOI guidance and updates on voluntary NIC contributions for those working abroad are also covered in the full update.
A useful third-party summary of the full Agent Update is available at rossmartin.co.uk.
Next Steps
Six items, six deadlines, and most of them fall before the end of July 2026. The mileage rate correction is retrospective and needs immediate payroll action. The CIS penalties are already accruing. The MTD quarterly deadline is weeks away. And the CT consultation closes tomorrow.
If any of these affect your business or portfolio and you need support, get in touch with Tanous. We work with PE-backed CFOs and finance directors to stay ahead of exactly this kind of compliance burden — so you can focus on running the business.