Multiconfiguration self-consistent field and multiconfiguration reference interaction including the Davidson's correction techniques were employed to calculate the potential energy curves (PECs) of the BeS/BeS+ electronic states correlating to the 4/5 lowest dissociation limits. After nuclear motion treatment, we deduced reliable spectroscopic data for the neutral and cationic bound states. For BeS, the transition moments and spin-orbit couplings were also evaluated and used later with the PECs to deduce the rovibronic transition probabilities and the radiative lifetimes in the low-lying states, and to investigate the unimolecular decomposition processes of BeS (X(1)Sigma(+), A(1)Pi, (3)Sigma(+) and B(1)Sigma(+)) leading to Be((1)S(g)) + S((3)P(g)). The prominent mechanism is a spin-orbit induced predissociation via the repulsive BeS(1(3)Sigma) state. Finally, we give the single ionization spectrum of BeS (X(1)Sigma(+)) populating the BeS(+) (X(2)Pi, 1(2)Sigma, 1(2)Sigma(+), 1(2)Sigma(+), 2(2)Sigma(+), 2(2)Pi and 3(2)Pi) electronic states. The adiabatic ionisation energy of BeS is estimated to be similar to 9.15 eV. (C) 2010 Published by Elsevier B. V.