Brunei–Malaysia border which are defined by agreements, from west to east, are as follows: Brunei and Malaysia in an Exchange of Letters on 16 March 2009, agreed to affirm the five agreements. The two countries also agreed to use the watershed principle to determine the remaining undelimited portions of the border. Brunei's maritime boundary with Malaysia until the 100 fathom isobath was inherited from the Sarawak (Definition of Boundaries) Order in Council 1958 No 1518 and the North Borneo (Definition of Boundaries) Order in Council 1958 No 1517, both of which defined the boundary between Brunei on the one hand, and Sarawak
Brunei–Malaysia border sections which were not covered by these agreements, the two countries agreed that their common border will be delimited based on the watershed principle. In addition, the two countries agreed to push for the joint demarcation and survey of their common border, through the establishment the necessary structures and processes to carry this out. The Memorandum of Understanding on the Process for the Joint Demarcation and Survey of the Land Boundary was signed on 19 March 2012 in Johor Bahru, Malaysia. The MOU, which was signed during the 8th Malaysia–Brunei Darussalam Meeting on the Implementation of the 2009 Exchange of