〜ことになっている
It is the rule that, it is scheduled thatmachine translation
FormationVerb dictionary form／ない-form + ことになっている
〜ことになっている expresses a rule, regulation, custom, or pre-set schedule that is still in effect: 教室では日本語だけを使うことになっている (by the rules, only Japanese is used in the classroom). This is the 〜ことになる you learned at N4 shifted into the ている form: the decision was made externally, and the state of "having been decided that way" still continues.
This pattern is very handy when you want to convey a rule objectively and gently — instead of commanding with 〜てはいけません, you simply say "that's just the rule here." It is also used for fixed appointments and finalized plans: 月曜日に社長と会うことになっています (as scheduled, I'm meeting the president on Monday).
Distinguish it from 〜ことにしている (from ことにする at N4): ことにしている is a rule you set for yourself (毎朝走ることにしている — I've made it my own rule to run every morning), while ことになっている is a rule or arrangement that comes from outside, which an individual can't change on their own.
Examples
日本では、車は道の左側を走ることになっています。
In Japan, cars are required to drive on the left side of the road.
来週の月曜日に社長と会うことになっています。
I'm scheduled to meet the president next Monday.
教室では日本語だけを使うことになっています。
The rule is that only Japanese may be used in the classroom.