A heat-sensitive recording sheet having a substrate with a heat-sensitive recording layer which contains color formers and color acceptors which react with one another under the action of heat. In order to permit the detection of counterfeited documents without the additional use of aids such as UV lamps or chemicals, present in the heat-sensitive recording layer, as a security element, are pressure-sensitive microcapsules which contain one or more color formers in a solvent. The color formers react with the color acceptors, forming a color, after destruction of the microcapsules.