Abstract The demand for Liquefied Natural Gas (LNG) as a marine fuel is surging as ship owners strive to comply with emission reductions set by the IMO. Transparency during bunkering operation is key to ensure acceptance by the different stake holders involved. The measurement equipment which is used today often misses on measurement traceability and custody transfer certification for the quantity measurement. Short deliveries and disputes between buyer and seller are the result. Complex and maintenance intensive gas analysis equipment is used to measure the LNG composition and requires frequent maintenance. This paper outlines the benefits of utilizing a custody transfer approved bunker metering system based on MFM (Mass Flow Meter) in combination with Raman spectroscopy. The transferred quantity of LNG is measured with custody transfer approved Coriolis mass flow meter of type Promass Q. This mass flow meter type has a mechanically optimized design for cryogenic liquids which leads to high temperature stability and accuracy. The quantity measurement includes LNG, boil off gas (BOG) and fuel gas consumption. Raman spectroscopy is used to measure the LNG composition in real-time without the need for vaporization and sampling. Custody transfer approved flow computers calculate the amount of energy transferred and provide the reporting for commercial transaction. In addition, the methane number is calculated following different mathematical models. The quantity measurement shows significantly better accuracy than required by OIML R117. The operation time is reduced due to real-time LNG composition measurement. This LNG bunkering system allows compact installation on board the bunker tanker because no vaporization and sampling equipment is needed. The Raman analyzer does not need any calibration gases for frequent verification. This reduces the effort and costs for maintenance. The real time quantity and quality measurement provides a high degree of transparency during the bunker operation. The combination of accuracy, transparency, custody transfer approval and real time information gives all stakeholder a high degree of confidence into the received measuring results. New is the combination of custody transfer approved MFMs with a Raman analyzer for metering LNG bunker transfers. The custody transfer certification for metering the LNG bunker quantities sets the corner stone for transparency and measuring accuracy. It lifts LNG bunkering on the same level of system integrity as we know it from the oil bunker industry using MFMs already today.Body text 1 paragraph.