When a meter's reading helps determine an exchange of goods, the question extends beyond how the instrument measures flow. The paperwork needs to identify the applicable controls and the purpose of each document. International type-evaluation evidence, a national code and verification of an instrument answer different questions. Reading them separately makes a specification easier to check and avoids treating every reference to a standard as the same kind of evidence.
What Legal Metrology Covers
Legal metrological control concerns measuring instruments subject to national or regional controls. The OIML-CS supports bodies responsible for type evaluation and approval, while Indonesia's verification rules identify uses such as business, handing over goods and determining levies or wages. For a flow-meter specification, begin by writing down what the measured quantity will be used to decide.
That description should be more precise than "fuel meter" or "water meter". Is the recorded quantity part of a transfer of goods, or is the instrument being considered for company control? Use that question to organise the documents rather than assuming the measuring principle settles the legal position.
OIML Recommendations and the OIML-CS
The OIML-CS introduction describes a voluntary system for issuing, registering and using certificates with associated type evaluation/test reports based on OIML Recommendations. OIML B 18:2025 sets out the rules under which signatories voluntarily accept and use that evidence for national or regional type approval or recognition. A useful document review therefore asks both what was evaluated and how that evidence relates to the intended national control.
The requirements for issuing authorities and associated test laboratories are the same in Schemes A and B, but the way compliance is demonstrated differs. Scheme B permits self-declaration with supporting evidence. Scheme A uses peer evaluation based on accreditation or peer assessment. Test laboratories must demonstrate compliance with ISO/IEC 17025. Scheme A is part of this voluntary system; it should not be described as a national legal requirement.
The OIML-CS category table places water meters under R 49, liquids other than water under R 117, and gas meters under R 137, all in Scheme A. Use the category to locate the relevant type-evaluation framework, then examine the actual documentation for the instrument being considered.
United States: NIST Handbook 44
NIST Handbook 44, 2026 edition, contains specifications, tolerances and other technical requirements for weighing and measuring devices, as adopted by the 109th National Conference on Weights and Measures. Its separate codes include liquid-measuring devices (3.30), vehicle-tank meters (3.31), LPG and anhydrous-ammonia liquid-measuring devices (3.32), water meters (3.36) and mass flow meters (3.37).
This division is a useful starting point for a document search: identify the measured fluid and duty, then locate the corresponding code. A specification that merely says "Handbook 44" leaves the reader to establish which of those different codes is intended.
Indonesia: Tera and Tera Ulang
The Ministry of Trade lists Permendag No. 24 Tahun 2024, dated October 2024, as in force. It governs tera, or initial verification, and tera ulang, or periodic re-verification. The regulation replaces Permendag 67/2018, 68/2018 and 125/2018. Its scope includes instruments used or kept ready for public interest, business, handing over or receiving goods, determining levies or wages, and determining a company's final product.
The official regulation abstract lists several places where tera can take place: a metrology technical unit, a laboratory or other test installation, the location of fixed instruments, an importer's warehouse for imported instruments, or a factory for domestic production. Verification activities include examination, testing and applying a verification mark or providing the specified written substitute. These are descriptions of the regulatory process.
Meters Kept Outside Trade
The Indonesian abstract specifies that instruments eligible for exemption from re-verification must bear "HANYA UNTUK KONTROL PERUSAHAAN" or "TIDAK DIGUNAKAN UNTUK BERDAGANG". These mean "for company control only" and "not used for trade". Keep the intended use and the required marking together when reviewing an exemption.
Do not infer exemption simply from an instrument being installed inside a company: the stated scope also includes determining a company's final product. The useful question is how the instrument is used and what evidence supports its treatment under the rules.
What to Ask for in the Paperwork
Arrange a review around three questions: what instrument category and intended use are recorded; what evaluation or test evidence is identified; and what national verification documentation is relevant? Keep the OIML Recommendation, any OIML-CS certificate and associated report, the applicable national code, and the instrument's verification record clearly identified.
For the earlier engineering questions about fluid, range and installation, return to the flow meter selection guide. Legal documentation is easier to assess when the proposed measurement duty is already described clearly.