The MSO does not simply require importers to hold a fixed volume of fuel. The obligation is individualised to each participant based on their own historical drawings, and expressed as a number of days of cover. The formula is defined in the Fuel Industry Regulations 2021, Regulation 32.

The days of cover required differ by fuel type and reflect a policy judgement about relative strategic importance and supply chain risk:

A critical feature of the compliance model is that it operates on a monthly average basis, not a daily minimum. An obliged person is not required to hold the minimum volume on every single day of a compliance period — they must hold it on average across the month. This provides operational flexibility: an importer may draw down stocks before a cargo arrives, provided the monthly average is maintained.

This distinction is rarely disclosed in public statements about the MSO. When a minister or official says "we require importers to hold X days of fuel," the implicit listener assumption is that this means every day. The reality is more nuanced — and more permissive.

Five companies currently import fuel into New Zealand and hold bulk storage access — making them obliged persons under the MSO. Each must submit a monthly compliance statement to MBIE by the 21st day of the following month.

The monthly compliance statement must declare whether the obliged person has met their stockholding obligation for the month, and if not, explain why and what remediation is planned. Importantly, importers must also retain evidence of how the information was gathered and calculated — the working documents behind the figure — for seven years.

The statement is self-certified. MBIE does not independently verify stock volumes before accepting the report. The regulator receives the declarations and cross-checks them against shipping data and other intelligence, but the primary source is the importer's own records. MBIE publishes aggregated national figures twice weekly — but individual importer positions are not published, as they are commercially sensitive.

The published figure — "52.2 days of diesel" — combines stock from two physically distinct sources. Understanding the difference matters in any disruption scenario.

The EEZ component — typically 1–2 days of cover — is physically real but not yet landed. A vessel inside the 200-nautical-mile EEZ boundary is 1–2 days from any NZ port and can be redirected quickly. This makes it countable for MSO purposes. Vessels outside the EEZ are inbound supply — real, planned, but not yet accessible.

The MSO counts only fuel held at registered bulk storage facilities with 1 million litres or more of capacity. Everything downstream of the terminal gate — once fuel is loaded onto a road tanker — exits the measurement boundary entirely. This is not a flaw in the design: the MSO was always intended to measure the wholesale layer. But it means the official figure systematically omits a large and physically real volume of fuel.

This stock is not a reserve. It is constantly cycling — drawn down and replenished — and cannot be mobilised as a coordinated emergency buffer. However, it represents real additional days of supply that would exist in the system during the early stages of a disruption, before it too is drawn down.

The agricultural fuel stock is particularly interesting. New Zealand has approximately 11,200 dairy farms and 23,400 sheep and beef farms — almost all of which carry diesel tanks for machinery. Under WorkSafe New Zealand rules, farms larger than 4 hectares may store diesel above-ground in tanks without a compliance certificate. This means tens of thousands of farm tanks, each holding 2,500–10,000 litres, exist in a completely unregistered, untracked, and uncounted state.

The MSO was designed explicitly to match what the fuel industry was already commercially holding — not to exceed it. This was a deliberate policy choice, documented in the regulatory impact statements, intended to minimise compliance costs and avoid requiring new storage infrastructure. The government's own assessment states that the minimum stockholding levels "do not immediately improve fuel security over the status quo — they ensure that fuel security does not deteriorate."

This means the 52-day figure, while technically correct, is not evidence of improved resilience. It is evidence that the status quo has been codified. Whether the status quo is adequate for a genuine disruption is a question the MSO was not designed to answer.

The government's fuel priority rationing framework — which determines who receives fuel first in a declared emergency — references "fuel" without specifying which layer of the distribution system it can draw from. If bulk terminal access is disrupted, priority access to fuel at that layer becomes meaningless. The retail station network, the farm tanks, the industrial customer sites — none of these are part of any formal priority allocation system.