As per the latest changes in MARPOL The bunker delivery note shall include a declaration signed and certified by the fuel oil supplier's representative that the fuel oil supplied is in conformity with regulation 18.3 of MARPOL Annex VI and that the sulphur content of the fuel oil supplied does not exceed the Sulphur limits.
Additionally, the fuel oil samples are always lab tested for suitability and compliance prior being used as per the management instructions.