CMP474​: Fixed BSUoS Price Revision Mechanism | National Energy System Operator

What this is about

CMP474 writes a Fixed BSUoS price revision mechanism into the CUSC. At present the Fixed BSUoS tariff is set for a defined period using NESO's forecast of balancing costs over that window, and there is no formal route to reopen the number mid-period if the forecast turns out to be wrong. NESO either over-recovers (and reconciles later) or under-recovers (and carries the financing strain). The modification proposes a documented process for NESO to reset the fixed price during the period when balancing cost outturn diverges materially from forecast, rather than leaving the reconciliation to the back end.

The driver is operational rather than philosophical. Balancing costs have been volatile and persistently above forecast across recent windows, the Fixed BSUoS arrangement is still in its early operating period, and the gap between the fixed price and underlying outturn has grown large enough that NESO is asking for a mid-window release valve. The modification has been put on the urgent track with an Authority decision: proposal in late April, four workgroup meetings between 30 April and 15 May, currently at Workgroup Consultation, sponsor Gregory Edwards. High impact has been flagged on Suppliers and Transmission System Operators, which is the right read: those are the two parties whose cashflows the reset would actually move.

The substance worth holding in mind while reading the rest. Fixed BSUoS was sold to suppliers as a hedge: a known, stable balancing cost they could price into fixed retail tariffs without carrying NESO's forecasting risk. A formal revision mechanism converts that hedge into a managed price with a reset clause. The reform reallocates forecasting risk away from NESO's cost-recovery line and back onto suppliers, and through them onto consumers on fixed deals. Whether that is the right answer depends on whether you think suppliers, NESO, or the consumer is best placed to bear short-run balancing volatility, and on how tightly the reset trigger is drawn. The detail of the trigger is therefore where the consultation matters, not the principle of having one.

Options on the table

The proposal form and workgroup materials referenced in the source list are not reproduced in the extract, so the precise menu of drafting variants the workgroup has converged on is not visible here. The workgroup consultation pack (CMP474 Workgroup Consultation and Annexes) will contain the original proposal and any Workgroup Alternative CUSC Modifications (WACMs). Respondents should read those before settling a position. What can be said from the framing is that the design space breaks down along four axes, and any WACM will sit somewhere on each.

Trigger design: rules-based vs discretionary

A rules-based trigger resets the Fixed BSUoS price automatically when a defined metric crosses a threshold, for example when forecast-to-outturn divergence over a rolling window exceeds a stated percentage or absolute £/MWh figure. A discretionary trigger gives NESO (or the Authority) the judgement call. Rules-based is more predictable for suppliers, which is the whole point of Fixed BSUoS; discretionary is more flexible for NESO, which is the whole point of asking for the mechanism. The hedge value of the fixed price is roughly inversely proportional to how much discretion sits in the trigger. Suppliers should push hard for a tight, numeric, externally verifiable trigger; NESO has an incentive to argue for headroom.

Reset frequency: one-shot vs repeatable within a window

A one-shot reset allows a single revision per Fixed BSUoS window. A repeatable mechanism allows multiple revisions if conditions continue to diverge. One-shot caps supplier exposure to a single shock event per window and is easier to price. Repeatable transfers the full forecasting risk back to suppliers and consumers and effectively unwinds the hedge: if NESO can reset whenever outturn moves, the fixed price is just a lagging spot price with administrative friction. The economically interesting variants are likely one-shot with a high trigger threshold, or repeatable with a tight collar on size of move per reset.

Direction: symmetric vs asymmetric

A symmetric mechanism resets the price both up (when outturn exceeds forecast) and down (when it undershoots). An asymmetric mechanism only resets upward, protecting NESO's cost recovery but not refunding suppliers when they are over-paying. Symmetric is the only version consistent with calling this a hedge mechanism. Asymmetric is a one-way put for NESO on supplier balance sheets, and should be called what it is. The workgroup will have views; respondents should check which variant the WACMs land on.

Pass-through and notice period

How much notice suppliers receive before a reset takes effect determines whether they can reprice fixed retail tariffs in flight or are left absorbing the reset on existing books. A short notice period (days to weeks) keeps the reset close to underlying conditions but lands the cost on suppliers' current customer base; a longer notice period (months) lets suppliers reflect the reset in new tariff books but leaves NESO carrying the gap in the meantime. This is the variable that matters most for the retail market, because it determines whether the cost stops at the supplier or is passed cleanly to consumers. Suppliers and Citizens Advice are likely to take opposite positions here.

Winners and losers across all variants. The consistent winner is NESO, which moves from carrying open-ended forecasting risk on its cost recovery to operating a defined reset process. TOs benefit on the demand-side BSUoS split where their cost recovery is tied to the same mechanism. The consistent loser is the supplier sector, which loses certainty on a price line they have already embedded in fixed-tariff offers; the size of the loss depends on how tight the trigger is and how long the notice period. Consumers on fixed tariffs are the ultimate bearer through pass-through, and only see this when their next fix renews. Consumers on variable tariffs see it sooner. None of this is hidden; it is the standard reallocation when an administered "fixed" price is given a reopener.

Questions being asked

The workgroup consultation response proforma and the WACM request form are listed in the documents but not reproduced in the extract. The specific numbered questions are therefore not visible. The questions a respondent should expect, based on the structure of CUSC workgroup consultations and the design space above, fall under the following themes. When the proforma is opened, the questions will sit roughly under these headings, sometimes split more finely.

Defect and need case

Whether the absence of a mid-period revision mechanism in the current Fixed BSUoS arrangement constitutes a defect in the CUSC, and whether the case for an urgent solution has been made. (This is asking whether you accept the framing that the status quo is broken, or whether you think the existing reconciliation arrangements at window-end are adequate. A "no" here is a respectable answer and stops the rest of the consultation.)

Trigger design

Whether the trigger should be rules-based or discretionary, and if rules-based, what metric and threshold should govern it. Whether the trigger should be symmetric (resets up and down) or asymmetric (resets up only). (The substantive question. Respondents who want to keep the hedge value should specify a numeric, symmetric, externally verifiable trigger and explain why.)

Reset mechanics

How many resets should be permitted within a Fixed BSUoS window. How the size of any reset should be calculated, and whether there should be a cap on the size of move per reset. What notice period should apply between a reset being announced and taking effect. (Notice period is the question that most directly affects supplier and consumer cashflows; do not leave it blank.)

Governance and oversight

Whether NESO should have unilateral authority to call a reset under the agreed rules, or whether each reset should require Authority approval or notification. What transparency and publication requirements should attach to a reset (data published, methodology disclosed, ex-post review). (This is asking how much you trust NESO with the discretion the mechanism creates. Stronger publication requirements are a cheap concession for NESO to offer and a meaningful one for the market.)

Treatment of existing contracts and consumer impact

How resets should be treated in supplier retail tariffs already in market, and whether any protection should apply to fixed-tariff customers whose contracts pre-date the reset. Whether the Authority should impose any constraint on pass-through to vulnerable consumers. (Largely a supplier and consumer-body question; expect divergent views.)

Implementation and timing

Whether the proposed implementation date is achievable and what transitional arrangements are required for the current Fixed BSUoS window. Whether the urgent procedure is appropriate or whether the modification should revert to the standard CUSC timetable. (A respectable answer here can be "the substance is right but the urgent timetable is wrong"; that disagreement is properly raised through this question rather than by attacking the modification itself.)

WACM and alternative drafting

Whether the legal text drafted in the proposal correctly implements the policy intent, and whether any WACMs should be raised. (Standard CUSC closing question. If you have a specific variant in mind that the workgroup has not produced, this is where you flag it.)

Respondents are encouraged, where they disagree with a design choice, to set out the alternative they would prefer rather than simply object. The Authority will weigh the modification, any WACMs, and the workgroup's assessment of which best meets the CUSC objectives. Responses that do not engage with the trade-offs above are easy for the workgroup to discount.

How to respond

The workgroup consultation is the current stage, with the consultation pack (CMP474 Workgroup Consultation and Annexes), response proforma (CMP474 Workgroup Consultation response proforma) and WACM request form (CMP474 Alternative Request Form) all listed on the NESO modification page (last updated 18 May 2026). The source extract does not include the closing date, the response email address, or the named contact for submission. These should be taken from the documents themselves before responding.

What is in the extract:

- Modification page contact: Code Administrator (email shown as redacted in source; resolve from the NESO CMP474 page directly) - Proposer: Gregory Edwards (email shown as redacted in source; resolve from the proposal form) - Governance route: Urgent modification under an Authority-agreed timetable, with an Authority decision - Current stage: Workgroup Consultation, following four workgroup meetings (30 April, 7 May, 11 May, 15 May 2026) - Documents to read first: CMP474 Proposal Form; CMP474 Workgroup Consultation and Annexes; CMP474 Workgroup Action Log; CMP474 Workgroup 4 Slides (15 May 2026)

Practical sequence for responding. Read the proposal form to anchor on the defect statement. Read the workgroup consultation pack and any WACMs to see how the trigger, frequency, symmetry, and notice period have been drafted. Read the workgroup action log to see which design questions are still live versus settled. Form a view on each of the themes above before opening the response proforma. Submit through the route specified in the consultation pack within the urgent timetable window. Given the urgent procedure, late responses are unlikely to be considered.

Suppliers with material Fixed BSUoS exposure in current retail books should respond. So should anyone who has priced the fixed tariff into customer offers on the assumption it would not move mid-window. Silence on this one will be read as acceptance of whatever variant the workgroup converges on.