Key code — A code that appears on response cards to identify the mailing when responses are mailed back, in order to track and analyze the effectiveness of the mailing.

Key code, generic — Response codes that help track the effectiveness of different media in a multi-media campaign.

Kill — To delete an electronic record or file.

Kill file — A file of names, used by a mailer, to eliminate undesirable contacts from a mailing list. This could be a list of people who have a pattern of nonpayment.