The dataset presented is part of the one used in the article "On solving the 1.5-dimensional cutting stock problem with heterogeneous slitting lines allocation in the steel industry" by María Sierra-Paradinas, Óscar Soto-Sánchez, Antonio Alonso-Ayuso, F. Javier Martín-Campo and Micael Gallego, in Computers & Industrial Engineering (2024), doi: https://doi.org/10.1016/j.cie.2024.110120. This paper proposes a mathematical optimisation model for a cutting stock problem in the steel industry. This problem appears in a Spanish company and the proposed model has been tested on real orders received by the company. The dataset presented here includes twelve instances used in the paper (the rest cannot be presented for confidentiality reasons). For each instance, the characteristics of the order and the solution obtained by the model are provided.