Formal procedures carried out when leaving a country at an airport/port, including passport checks, immigration exit procedures, and boarding formalities.
出国手続きを済ませてからラウンジで休んだ。
I rested in the lounge after completing the departure procedures.
出国手続きにはパスポートの有効期限に注意が必要だ。
You need to pay attention to your passport's validity when completing departure procedures.
長い列のため出国手続きに時間がかかった。
Departure procedures took a long time because of the long line.