A formal expression meaning that something has been decided or arranged to be so ("it has been decided that..."). Often used in official or formal contexts.
来月から勤務時間を変更することとなりましたので、ご了承ください。
Please be advised that it has been decided to change working hours starting next month.
社内で検討した結果、契約を更新しないこととなった。
After internal review, it was decided not to renew the contract.
双方の合意により、予定通り開催することとなる。
By mutual agreement, it has been decided to hold the event as scheduled.