What are the rules when I tack or change course?

While tacking (rule 13): after a boat passes head to wind she must keep clear of other boats until she is on a close-hauled course. During that time rules 10, 11 and 12 do not apply. If two boats are subject to this rule at the same time, the one on the other's port side or the one astern keeps clear.

Changing course (rule 16.1): when a right-of-way boat changes course, she must give the other boat room to keep clear.

Beating to windward (rule 16.2): when a port-tack boat is keeping clear by passing to leeward of a starboard-tack boat, the starboard-tack boat must not bear away if that would force the port-tack boat to change course immediately to keep clear.

Acquiring right of way (rule 15): when you gain right of way, you must at first give the other boat room to keep clear, unless she gained it through the other boat's own actions.

Source: Racing Rules of Sailing 2025-2028 with Australian Sailing prescriptions, rules 13, 15 and 16.