indicates that something has been arranged, taken care of, settled, or completed. When used as a suffix it is typically pronounced “-zumi” (e.g., 支払い済み).
この書類は提出済みですから、もう心配いりません。
This document has already been submitted, so you don't need to worry anymore.
配送料金は前払い済みになっています。
The shipping fee has been prepaid.
見積もりは確認済みだが、まだ発注していない。
The estimate has been checked, but the order hasn't been placed yet.
予約済みの席は出口付近です。
The reserved seat is near the exit.