The main rate writing-down allowance for plant and machinery dropped from 18% to 14% on 1 April 2026. It is not a proposal. It is not pending. It is in force now, affecting every accounting period that started on or after that date. If your finance team has not updated its tax modelling, your deferred tax balances are wrong and your capital expenditure business cases are being evaluated against a rate that no longer exists.
Alongside that structural change, the Upper Tribunal’s April 2026 decision in CATS North Sea Ltd v HMRC [2026] UKUT 142 (TCC) has just resolved a £167 million capital allowances dispute with a result that should be required reading for any CFO involved in complex group restructurings. The Tribunal cut the balancing charge from HMRC’s claimed £167m to just £23m — a £144m swing — on the basis that HMRC had fundamentally misapplied the interaction between oil and gas ring-fence deeming provisions and the intra-group transfer rules in Part 22 CTA 2010.
Together, these two developments crystallise why capital allowances planning has moved up the boardroom agenda in 2026. The rules are more complex, the stakes are higher, and the margin for error is greater than at any point in the last decade.
What Changed on 1 April 2026
The Autumn Budget 2025 announced a two-part reform to capital allowances that is now in effect. First, the main pool writing-down allowance rate has been cut from 18% to 14%. Second, a new 40% first-year allowance (FYA) was introduced from 1 January 2026, applying to main rate plant and machinery including — critically — assets used for leasing, which were previously excluded from full expensing.
The special rate pool (long-life assets, integral features) is unaffected and remains at 6%. But for the bulk of capital expenditure that sits in the main pool — machinery, equipment, IT hardware, vehicles, general fixtures — the annual deduction is now permanently lower.
The practical arithmetic is straightforward but the impact compounds. On a £10 million opening main pool balance:
- Under 18%: year-one deduction of £1.8 million
- Under 14%: year-one deduction of £1.4 million
- The difference — £400,000 of deferred relief — feeds directly into higher taxable profit at 25%
Across three years, a business with a £10m legacy pool loses approximately £1.1 million in cumulative tax relief compared with the old regime, simply because of the rate change. That is real cash. It needs to be in your tax forecasting models.
The Hybrid Rate Problem for Straddle Periods
One complication that will catch businesses out is the hybrid rate for accounting periods that span 1 April 2026. If your year-end is 31 December, your period from 1 January to 31 December 2026 straddles the change date. You do not simply apply 14%. You apply a blended rate: 18% for the days before 1 April 2026, 14% for the days from 1 April onwards, weighted by time.
For a December year-end company: approximately 90 days at 18% and 275 days at 14%, giving an effective rate of approximately 14.9%. Your tax software should handle this automatically — but it needs to be configured correctly. Test it before your CT600 goes in.
PwC’s UK corporate tax summary confirms the hybrid rate mechanism and also highlights the interaction with the new 40% FYA: businesses can avoid the WDA rate reduction entirely on new qualifying expenditure by claiming the FYA instead, which effectively replaces the need to run a separate calculation on eligible assets.
The New 40% First-Year Allowance: Who Benefits and Who Doesn’t
The 40% FYA deserves more attention than it has received. It applies to expenditure incurred from 1 January 2026 on main rate plant and machinery — including assets for leasing — but excludes second-hand assets, cars, and assets leased overseas. For a business spending £5 million on new qualifying plant, the FYA gives a £2 million first-year deduction instead of the £700,000 you would have received under the new 14% WDA rate.
The leasing inclusion is the most commercially significant element. The previous restriction on full expensing for lessors was a significant planning headache. Its removal means leasing businesses, hire companies, and asset finance providers can now front-load relief on new assets acquired for their core business. The Government had consulted on this change — its delivery confirms a structural shift in how the UK treats capital-intensive leasing businesses for tax purposes.
What the 40% FYA does not fix is the legacy pool problem. If you have existing pool balances built up over years of investment, those assets are stuck on the 14% treadmill. The new FYA only helps on new qualifying expenditure. Historic pools get no relief acceleration.
CATS North Sea Ltd v HMRC [2026] UKUT 142: The £144 Million Lesson on Deeming Provisions
The CATS North Sea case is the kind of decision that should be read by every tax director involved in group reorganisations — not because most businesses operate North Sea pipelines, but because the analytical error HMRC made is one that recurs in virtually every complex restructuring: treating a statutory deeming provision as if it creates a single unitary trade when the legislation, read carefully, creates multiple deemed part-trades with different characteristics.
The facts in outline: Amoco (a BP Group company) transferred its interest in the Central Area Transmission System pipeline — a major North Sea hydrocarbon transport asset — to its subsidiary CATS North Sea Ltd (CNSL) for £1 in a hive-down, then sold the shares in CNSL to a third party, Kellas. HMRC argued this triggered a balancing charge of £167 million. CNSL argued the correct figure was £23 million.
The legal pivot was the interaction between section 279 CTA 2010 — which deems oil-related activities to be a separate trade for ring-fence purposes — and Part 22 CTA 2010, which provides for the intra-group continuation of capital allowances pools on a transfer of trade. HMRC said Part 22 applied to the entire transfer. The Upper Tribunal said it only applied to the part of the trade that remained Inside Ring Fence for both transferor and transferee — which, once CNSL ceased to be associated with Amoco after the share sale, was a much smaller fraction of the asset value than HMRC contended.
The £144 million difference between the two positions is not a rounding error or a technicality. It is the direct result of correctly disaggregating the deeming analysis: treating the IRF and ORF components as separate part-trades for capital allowances pooling purposes, rather than running them together as HMRC sought to do.
Jonathan Peacock KC, instructed by Freshfields, succeeded for CNSL. HMRC was represented by Jonathan Bremner KC. The Upper Tribunal found that the First-tier Tribunal had made a fundamental error in its statutory analysis.
What CATS North Sea Means Outside the Oil Sector
The significance of this decision extends well beyond North Sea operators. The analytical framework — how deeming provisions interact with continuation rules, and whether a “deemed trade” for one purpose is necessarily a “deemed trade” for another — is directly relevant wherever you have:
- A business that is ring-fenced or hived down ahead of a sale
- Intra-group transfers of capital-intensive assets followed by a disposal of the vehicle
- Any transaction where Part 22 CTA 2010 might apply, particularly where the transferred business is not entirely homogeneous
- PE structures involving step-up hive-downs to create a clean acquisition vehicle
If your restructuring advisers are relying on a blanket application of Part 22 without separately analysing the constituent parts of the trade being transferred, CATS North Sea is a direct warning. HMRC got this wrong at the FTT level and had it overturned at the UT. The implication is that the same analytical failure could be made in the other direction — understating a balancing charge where Part 22 should not have applied at all.
Late Filing Penalties Also Doubled on 1 April 2026
A point that has received relatively little attention alongside the WDA changes: the fixed penalties for late corporation tax returns also doubled on 1 April 2026. The penalty for filing a company tax return one day late is now £200 (previously £100). The additional penalty at three months is a further £200 (previously £100). These are not significant sums for most businesses, but the doubling signals a direction of travel: HMRC is progressively hardening the consequences of late compliance across multiple taxes simultaneously.
In conjunction with the MTD for IT deadlines coming into force next year, the message from HMRC is consistent: the era of low-cost non-compliance is ending. Build in the buffer time for filings that currently sail close to the deadline.
Six CFO Actions Before Your Next Year-End
1. Remodel your deferred tax balances now. If your year-end is between April and December 2026, your opening deferred tax calculation used 18%. Your closing calculation uses 14% (or a hybrid). The difference flows through P&L as a deferred tax charge. Your auditors will want this analysed before fieldwork begins. Do not leave it to Q4.
2. Audit your legacy main pool balances. Businesses with material historic expenditure sitting in the main pool — manufacturing plant, distribution equipment, IT infrastructure — face the most significant cash impact from the rate reduction. Quantify the pool balance and model the annual cash cost of the slower relief trajectory. If the numbers are large, it may be worth bringing capital expenditure forward to claim the 40% FYA rather than allowing assets to trickle through the pool at 14%.
3. Review every piece of new capex for 40% FYA eligibility. The 40% FYA is not automatic — you need to claim it, and it applies to qualifying new main-rate assets only. Second-hand assets, cars, and overseas-leased assets are excluded. Build FYA assessment into your capex approval process for any new expenditure from 1 January 2026 onwards. Consult HMRC’s capital allowances guidance and your tax advisers on the eligibility conditions.
4. If you lease capital assets, this is your year to act. The extension of the 40% FYA to assets held for leasing is a structural tax advantage that did not exist before January 2026. If you run a hire or leasing book, model the benefit of accelerating qualifying asset purchases to capture the FYA before the Government changes course. The Autumn Budget 2025 documentation sets out the policy intent, but the window for accelerated relief is now.
5. Stress-test any hive-down or intra-group transfer for CATS North Sea-type issues. If you have a planned restructuring involving the transfer of capital-intensive assets between group companies — particularly where the business being transferred has different components that might be treated differently under any ring-fence or sectoral deeming provision — get specialist capital allowances advice before completion. The UT’s analysis in CATS North Sea makes clear that the capital allowances treatment of a transfer is not a binary question. It depends on the statutory character of each part of what is being transferred.
6. Check your special rate pool separately. The 6% special rate remains unchanged, but the absolute value of that rate matters more now that the main pool rate has dropped. Assets that were borderline between main pool and special rate classification — some integral building features, certain long-life assets — may now need reclassification review if capital expenditure decisions were made on the basis of the old 18% main rate.
The Broader Picture on Capital Allowances Strategy in 2026
Capital allowances have always rewarded businesses that engage with the detail rather than accepting the default. The 2026 changes make that more true than ever. Full expensing and the annual investment allowance (£1 million) remain available for businesses that qualify — and for most SMEs with capital expenditure below the AIA threshold, the WDA rate change is largely irrelevant because their spending will be fully expensed anyway.
The businesses most exposed to the 14% rate are those with large historic pools and those whose expenditure exceeds the AIA threshold or falls outside full expensing categories. For PE-backed businesses with significant fixed asset bases, the deferred tax impact on exit multiples is worth modelling explicitly. A buyer acquiring a business in late 2026 is acquiring a deferred tax liability calculated at 14% rather than 18%, which affects the quality of the balance sheet.
The ICAEW capital allowances guidance and the CIOT’s technical resources on capital allowances are both worth reviewing if you want a practitioner-level walkthrough of the current rules. For complex situations — particularly those involving intra-group transfers, leasing, or multi-component assets — specialist input is not optional.
Talk to Tanous
Capital allowances planning in 2026 requires a complete reset of assumptions built over years of stable 18% WDA rates. If your business has significant fixed asset pools, is planning material capital expenditure, or is involved in any group restructuring where capital allowances are a factor, now is the time to remodel.