The invention relates to a plaster, in particular a transdermal, preferably therapeutic system comprising: a cover film a layer (matrix layer), consisting of or comprising a matrix that contains an active ingredient and is optionally self-adhesive a facultative self-adhesive layer of adhesive, or an obligatory self-adhesive layer of adhesive (if the matrix is not self-adhesive) and a one-piece peeling film, said film being provided with a groove on the side facing the matrix layer.
