Provided is a microporous material, e.g., a microporous sheet material, having a matrix of polyolefin, finely-divided, substantially water insoluble particulate filler, a network of interconnecting pores communicating throughout the microporous material, and at least one retrospectively identifiable taggant material embedded within the matrix, optionally the at least one taggant being unique to an end user for the microporous material, wherein the polyolefin is present in the microporous material in an amount of 20 to 35 weight percent, based on the weight of the microporous material. The taggant material provides a marker, signature or code that is capable of retrospective identification by machine, instrument or by the naked eye. Articles including the microporous material and processes for preparing the microporous material also are provided.