Disclosed are methods of using a transparent, luminescent polymer for transparent marking and/or labeling for identity verification purposes. Also disclosed are sheets, films, markers, labels and taggants comprising transparent, luminescent polymers. Also disclosed are articles labeled with a transparent, luminescent polymer. This invention particularly relates to use of transparent, luminescent polymer compositions comprising ethylene (meth)acrylic acid copolymers and rare earth ions and transparent, luminescent polymer compositions comprising methyl (meth)acrylate/(meth)acrylic acid copolymers, fatty acids and rare earth ions for these purposes.