Abstract. In many practical business process modelling scenarios using Petri nets, the resultant model does not have a single input place and a single output place. In particular, this happens when the Petri net model is derived by mapping from an Hybrid IDEF0-IDEF3 model. Therefore, the correctness of the model cannot be assessed with existing techniques, which are devised for WF-nets — a special class of Petri nets with a single input place and a single output place. Moreover, the existing approaches for tackling this problem are rather simplistic and fail to work even for some simple cases. We show that, by an appropriate reduction of a multiple input/multiple output Petri net, existing techniques can be used to check the correctness of the original process. The approach is demonstrated with a suitable example.