per kerende (vaste woordgroep)
per kerende post, per ommegaande, onmiddellijk, stande pede, per direct, terstond

Gevraagde stukken per kerende.
Gelieve per kerende de bevestiging van onze bestelling te mailen.

(https://www.vlaamswoordenboek.be/definities/term/per%20kerende)
* per kerende fax; per omgaande fax = by return fax
* per kerende post = by return post; by return of post (UK); by return mail (US)
(Juridisch-Economisch Lexicon, Aart van den End) 

Dutch

  • per kerende

English

  • by return e-mail
  • by return mail
  • by return e-mail
  • immediately
  • without delay
  • at the earliest opportunity