The article proposed and justified the need for on-line calibration, the essence of which is to conduct individual calibration in real time directly at the place of operation of gas meters, taking into account the conditions and influential factors for which they conduct measurements to determine the actual calibration characteristics. This procedure should be one of the primary tools in ensuring widespread adoption of Metrology 4.0. It was noted that the key direction of development of the metrology industry should be the conformity assessment of the gas control and metering system. The given example of calculations (Table 1) carried out in assessing the compliance of such a system. It was found that the greatest weight has the error of the gas meter. In order to carry out the on-line calibration procedure, it is proposed to use the installation with parallel installed reference meters (Fig. 1), which is designed as a mobile stand with the ability to be transported to the work site. The necessity of on-line calibration is justified on the example of the obtained characteristics of gas meters (Fig. 2, Fig. 3). The results of the gas meter calibration on the working environment natural gas (Fig. 4) are presented and the total uncertainty of the gas metering system is calculated (Table 2). The application of the on-line calibration procedure leads to the need to develop the concept of introducing intelligent or smart metering of natural gas using intelligent information-measuring systems. As part of the implementation of smart metering, the possible introduction of two-tariff metering of natural gas. As a tool for statistical processing of the data, it has been proposed to apply control charts that have been tested for reference standards and are recommended in international documents.