The Single Source Regulations Office has issued its first consolidated guidance on redetermining the price of a qualifying defence contract or qualifying sub-contract, bringing together rules previously dispersed across legislation and other guidance. The regime that guidance interprets governs the largest single channel of British defence procurement: the Ministry of Defence placed £18.4 billion non-competitively in 2024/25, forty-five per cent of Core Department payments and, in the Department’s own words, the predominant procurement method for the third consecutive year. Against that annual flow, the entire regulated population accumulated since April 2015 carries a total estimated contract price of £140.1 billion, of which the contracts that have actually completed and permit a price comparison account for £18.6 billion. A defence order within that channel can remain militarily necessary while the specification, quantity or delivery schedule on which its price was agreed becomes unsuitable. The purchaser may need an earlier delivery, an additional batch, different equipment or continued support for longer than expected. The supplier may need to change working arrangements, hold materials or commit resources before the commercial consequences are settled. Each adjustment raises a question about the economic content of the existing order: which obligations and risks were already paid for, and which require a new agreement? For European defence, this is part of the problem of sustaining industrial demand over time. An order provides a more durable basis for production when its terms accommodate necessary adaptation, but accommodating adaptation also requires a way to establish who bears its cost. No published dataset answers that question in the aggregate, and the reason it does not is itself part of the subject.