Formal to Client
Workplace · Email
You
ご連絡が遅くなりましたこと、誠に申し訳ございませんでした。
ごれんらくがおそくなりましたこと、まことにもうしわけございませんでした。
I sincerely apologize for the delay in getting back to you.
Romaji: Go-renraku ga osoku narimashita koto, makoto ni moushiwake gozaimasen deshita. / Reply Romaji: Ie, daijobu deshita yo.
Reply
いえ、大丈夫でしたよ。
いえ、だいじょうぶでしたよ。
Oh, that's alright.
Gesture & etiquette
Email context — place the apology as the very first sentence, before even 「お世話になっております」. Brevity in the apology is appropriate — do not over-elaborate, which can feel performative.
A late reply in Japanese business requires a formal apology — begin every late response with this phrase before any content. 「誠に申し訳ございませんでした」uses past tense to acknowledge the completed transgression. Following with a clear, efficient response to the original message is the best way to restore goodwill.