This structure can also be seen with the verb “to become”. Here the meaning is that “it has been decided that…” and is used when the outcome is something that you haven’t decided yourself.
来週は、出張へ行くことになりました。
Next week it has become the thing that is going on a business trip
Often the verb “to become” takes the present participle form which roughly translates as “supposed to be such that”. It is used to state that the prior clause is a rule that must be followed.
～ことになっている is JLPT N3 grammar. Can be used in both writing and conversation, but there are more formal ways of creating this expression.
うちの会社では、パソコンをなくすと謝罪文を書くことになっています。
In my company, you need to write an apology if you lose your computer.
こちらではタバコを吸えないことになっているので、ご協力お願いします。
You cannot smoke here. We ask for your co-operation.
私がいないときに荷物が届いたら、宅配ボックスに入れてもらうことになっています。
If the parcel arrives at a time when I’m not home, then they’re supposed to put it in the delivery box.