Formal to Client
Workplace · Email
このたびはご協力いただきまして、誠にありがとうございました。 — Thank you very sincerely for your cooperation on this occasion. (Workplace · Email, Formal to Client, JLPT N3)
You
このたびはご協力いただきまして、誠にありがとうございました。
このたびはごきょうりょくいただきまして、まことにありがとうございました。
Thank you very sincerely for your cooperation on this occasion.
Romaji: Kono tabi wa go-kyouryoku itadakimashite, makoto ni arigatou gozaimashita. / Reply Romaji: Ie, kochira koso. Mata yoroshiku onegai itashimasu.
Reply
いえ、こちらこそ。またよろしくお願いいたします。
いえ、こちらこそ。またよろしくおねがいいたします。
Not at all. Likewise, I look forward to working together again.
Gesture & etiquette
Email context — no gesture. If the cooperation was especially significant, consider a follow-up phone call or even a small gift (手土産) at the next in-person meeting as an additional expression of gratitude.
Gratitude emails are an essential part of Japanese business relationship maintenance. 「このたびは」(on this occasion) ties the thanks to a specific event, making it personal rather than generic. Send this within 24 hours of completing a project or receiving help — timely thanks is highly valued.