[header] How to kosher liver [title] Be particular about the liver you buy. [step] The liver should come from a kosher species (cow, calf, or chicken) that was slaughtered in the matter described by the torah. [substeps] The fats of the liver should have been removed during the time of slaughter. 
Ideally, you should purchase liver from an animal that was slaughtered no more than 72 hours ago. The koshering process itself should be performed within 72 hours.