What it means
ことになる expresses that something has been decided, arranged, or has come to be the case because of circumstances. It often presents the result as something determined by a group, another person, or outside conditions rather than as the speaker’s own direct choice. It follows a plain-form verb, including a negative verb when the decision is not to do something.
Usage note
Do not confuse ことになる with ことにする. ことにする presents a decision made by the subject, while ことになる presents a decision or result that is settled by circumstances or someone else. When referring to a decision that was already made, the past form ことになった is often more natural.
How to use it
来月から東京で働くことになります。
It has been decided that I will work in Tokyo from next month.
今年は海外へ出張しないことになります。
It has been decided that I will not go on a business trip overseas this year.
来月から東京で働くことになる。
It has been decided that I will work in Tokyo from next month.
今年は海外へ出張しないことになる。
It has been decided that I will not go on a business trip overseas this year.