G-CTMQC module provides numerical tools to perform simulations of internal conversion (spin-allowed) and intersystem crossing (spin-forbidden) phenomena underlying photochemical and photophysical reactions. G-CTMQC gives the user the flexibility of employing different approaches and, thus, various approximation schemes, to achieve dynamical information as accurate as possible, as well as ample flexibility in the choice of systems that be studied thanks to the interface of G-CTMQC with QuantumModelLib (E-CAM module).