Abstract: Systems and methods for credit card relationship derivation from historic data are provided. A single credit card relationship between a membership organization and a member can be very long-lived and identified by many different account numbers over time. For example, a new card with a new number can be issued if the card is lost, stolen, the member changes the card type (Standard, Gold or Platinum) or the card number is thought to be compromised. Sometimes, data security compromises committed by third-parties can result in a simultaneous mass re-issue of many cards. Various embodiments of the present invention create a common key and ordinal numbers that identifies the account throughout its life by resolving ambiguities and inconsistencies in historical data.