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 line. Malaysia's submission was jointly made with Vietnam where both countries claimed a "defined area" over which both countries currently have overlapping claims. Brunei should also have a competing claim over a portion of the "defined area". However, unlike China and the Philippines which objected to the Malaysia-Vietnam joint submission, there is no record of Brunei registering any similar objection. Brunei has not submitted its extended continental shelf claim to Commission on the Limits of the Continental Shelf. However, in its preliminary submission which it lodged with the Commission on 12 May 2009, it gave notice of its intention to