失礼いたします (Shitsurei itashimasu) means "Excuse me" and is a formal and humble version of 「失礼します」. You use it when entering or leaving a room, ending a phone call, or politely interrupting someone, showing respect and acknowledging a potential intrusion.

部屋の出入り、電話を切る際、少し邪魔をする時などに使う、丁寧な「失礼します」です。