Draft legislation to make the foreign permanent establishment (FPE) exemption mandatory is no longer a summer briefing note. For oil and gas groups with overseas branches, the accelerated start is 1 September 2026 — three calendar days from this post. For everyone else, the default is accounting periods beginning on or after 1 January 2027. Technical comments on the L-Day draft close on 13 September 2026.
Primary sources: the GOV.UK reform pack and accessible draft legislation, the original May 2026 policy paper, Deloitte’s August 2026 TaxScape update, BDO’s FPE briefing, KPMG’s Tax Matters Digest note, ICAEW’s May summary, and Bloomberg Tax’s late-August corporate-regime analysis. If your ETR model still assumes elective branch exemption and free UK relief for overseas branch losses, rewrite it this week.
What actually changes
Since 2011, a UK-resident company could elect under CTA 2009, Chapter 3A so that profits and losses of foreign permanent establishments dropped out of the UK corporation tax computation. The election was irrevocable and applied to all foreign branches of that company. No election meant worldwide taxation with double tax relief; election meant territorial treatment of the branch.
The draft removes the choice. Qualifying FPE profits and losses are automatically excluded. There is no more opt-in, no more staying on the worldwide basis to harvest UK relief for overseas start-up losses, and no more “we will elect later when the branch turns profitable” narrative. The policy objective is blunt: stop the UK Exchequer underwriting overseas investment via UK loss relief and capital allowances when future foreign profits never effectively return to the UK net — either because double tax relief covers them or because the activity is incorporated into a non-UK subsidiary before the profit years arrive.
That is a structural territorial shift, not a tidy-up. BDO and KPMG both flag the same cash consequence: higher UK taxable profits, higher current tax, and more ETR volatility for any group that has been netting foreign branch losses into the UK.
Oil and gas: 1 September is not a soft date
The Chancellor’s May announcement and the firm commentaries are consistent on the sector acceleration. Where a UK-resident company carries on oil and gas exploration or exploitation through a foreign PE, the mandatory exemption is brought forward to 1 September 2026, typically by deeming an accounting period to end on 31 August 2026. That is not a modelling nicety. It forces an artificial year-end, a short-period CT computation, capital allowance cut-offs, loss-allocation work, and immediate cessation of UK relief for post-31 August overseas branch losses.
If you have North Sea-adjacent overseas branches, exploration joint ventures booked as PEs, or capital-heavy overseas development assets sitting in a UK company, the board conversation should already have happened. If it has not, the conversation this Monday is late.
TONA dies; transitional allocation takes over
Under the old elective model, groups that entered exemption faced the total opening negative amount (TONA) regime — a clawback mechanism for pre-election foreign branch losses. The draft repeals sections 18J–18O CTA 2009 and replaces that architecture with detailed transitional rules in Schedule 2.
Those transitional rules will matter more than the mandatory label for many CFOs. In outline:
- Carried-forward income losses attributable to foreign PEs in a lookback window are restricted from set-off against post-commencement UK profits (with limited carve-outs).
- Carried-forward capital losses get equivalent treatment.
- Capital allowances require identification of assets attributable to foreign PEs, removal from UK pools without automatic balancing charges in the core case, and careful handling of high-value assets in a lookback window where balancing adjustments can still arise.
Bloomberg’s Haynes Boone analysis is right on the practical point: for many groups, the allocation exercise on historic losses and plant pools will dominate the project plan. This is not a one-line CT return toggle. It is a workstream for tax technical, fixed-asset accounting, and the ERP owner.
Anti-avoidance already runs from 13 July 2026
Do not wait for 2027 to respect the guardrails. Draft section 5 counteracts foreign-PE-related avoidance arrangements where the main purpose includes accelerating recognition of income, expenditure, profit or loss into a pre-commencement period, or otherwise gaming commencement. The timing test catches arrangements coming into being on or after 13 July 2026 (L-Day), or pre-L-Day contingent arrangements formalised after that date. Condition C is an abuse test aimed at contrived or non-commercial steps.
There is also a short-accounting-period anti-avoidance rule that can pull commencement forward where companies try to manufacture short periods between L-Day and 1 January 2027. If someone in the group has already suggested “we’ll just shorten the AP to lock losses,” park that idea and read section 7 of the draft.
PE definition moves to the treaty / OECD model
New section 18RA CTA 2009 would determine whether there is a foreign PE by reference to the relevant double tax treaty, or otherwise the OECD Model, rather than the domestic CTA 2010 Chapter 2 definition that generally applies for corporation tax. That alignment is sensible for international consistency, but it is not neutral. Groups that have been running a domestic-definition PE analysis for branch exemption purposes need to re-map every territory against the treaty article (or OECD fallback) before they sign off “we have no PE” positions used to stay outside the new mandatory world.
Expect more HMRC attention on profit attribution, agency PE, and service PE facts. The more the UK locks into territorial branch treatment, the more the audit question becomes “is this really a PE, and are the profits correctly attributed?”
Knock-ons CFOs actually feel
R&D and Patent Box. Expenditure and IP profits sitting in a foreign PE that is now mandatorily outside UK CT can fall out of UK incentive regimes. The draft’s consequential amendments already touch Patent Box qualifying expenditure mechanics. Re-run R&D roadmaps where competent professionals and cost centres sit overseas under a branch model.
CFC and anti-diversion. Moving activity from branch to subsidiary to “solve” the loss problem can create or enlarge CFC exposure. The old FBE anti-diversion flavour remains relevant; do not trade one problem for another.
Pillar Two. Branch profits and losses dropping out of UK CT computations change jurisdictional ETR arithmetic. Separately, if you still have a GloBE Information Return that failed validation, HMRC’s extended fix window ends on 1 September 2026 — see the live Pillar Two reporting guidance. That deadline collides with the oil and gas FPE start. One weekend, two clocks.
Branch versus subsidiary. The elective edge that once made branches attractive for early-year UK loss relief is being removed. Local withholding tax, exit charges on incorporation, CFC, treaty access, and substance tests now dominate the structure memo. Refresh every live “keep it as a branch” paper before Budget season.
Transfer pricing. Attribution under OECD TP principles becomes the battleground once losses no longer wash through the UK. Document people functions, risk control, and capital attribution properly. For PE groups also watching treaty interest withholding simplification, the parallel WHT treaty-relief consultation closes on 7 September 2026.
What every CFO should lock this week
- Inventory every foreign PE — legal entity, territory, treaty article, activity (flag oil and gas), and whether any CTA 2009 s18A election is live.
- Oil and gas short period — if in scope, force the 31 August / 1 September split into the CT calendar, capital allowance engine, and consolidation pack now.
- Loss and CA allocation workstream — stand up the Schedule 2 lookback exercise; do not leave it to the 2027 CT return cycle.
- Anti-avoidance hygiene — freeze any pre-commencement loss-acceleration or short-AP planning that fails the 13 July purpose tests; minute commercial rationale.
- Model cash tax and ETR — base case, oil and gas accelerated case, and branch-to-subsidiary alternative; take the bridge to the audit committee.
- Incentive and Pillar Two overlays — R&D, Patent Box, CFC, and GIR status on the same dashboard as the FPE project.
- Respond by 13 September — if the draft creates genuine commercial friction (lookback length, CA balancing, PE definition edge cases), send a focused note to foreignpepolicy@hmrc.gov.uk while the window is open.
- Systems — confirm the ERP/tax engine can tag FPE amounts, suppress UK relief post-commencement, and produce the allocation audit trail HMRC will expect on enquiry.
Bottom line
The UK is finishing the job on territorial corporation tax for foreign branches. Elective exemption rewarded groups that could take UK relief on the way down and keep foreign profits lightly taxed on the way up. Mandatory exemption ends that asymmetry. Oil and gas hits first on 1 September 2026. Everyone else has until periods starting on or after 1 January 2027, but the anti-avoidance rules and the transitional homework are already live issues.
Treat this as a cash and structure programme, not a technical newsletter. Map the PEs, model the lost UK loss relief, clear the capital allowance pools, and decide whether the branch still earns its keep against a subsidiary. The groups that wait for the Finance Bill reprint will spend 2027 explaining variance. The groups that lock the checklist above will own the narrative.
This article is general information for CFOs and finance leaders, not advice on any specific structure or return position. Take advice on your facts before changing PE classification, loss claims, or branch/subsidiary form.