Official approval was legally required for any transfer of title, and land belonging to the indigenous people could not be sold at all, but it was possible to bypass the regulations--to evade tax or to obtain reservation land--with private agreements known as "white contracts," in contrast to the "red contracts" that carried the seal of official approval.
會產生找價行為，主要是因為依照清規，土地的轉賣必須經過官方許可，而原住民的土地則是不可買賣的。只是民間或是為了逃稅或非法擁有熟番保留地，因此相互立下契約稱做「白契」，不同於向官方登記合法的「紅契」。