The aim of being able to reason about quantities, time, space and much more has been the main objective of the many efforts on the integration of propositional planning with extensions to handle different theories. Planning Modulo Theories (PMT) is an approximation inspired by Satisfiability Modulo Theories (SMT) that generalizes the integration of arbitrary theories with propositional planning. Parallel plans are crucial to reduce plan lengths and hence the time needed to reach a feasible plan in many approaches. Parallelization of actions relies on the notion of (non-)interference, which is usually determined syntactically at compile time. In this paper we present a general semantic notion of interference between actions in PMT. Along its generality, this notion can be efficiently checked at compile time by means of satisfiability checks.