Ab initio computations have been performed to investigate the stability and the spectroscopy of the HNCl(-) anion. Using explicitly correlated coupled-cluster methodology and core-valence basis set, the linear-bent path of the neutral and anionic molecules have been computed, and the adiabatic electron affinity of HNCl has been deduced at 1.29 eV. The three-dimensional potential energy surface of the neutral HNCl ((X) over tilde (2)A '') and of the HNCl(-) ((X) over tilde (1)A') anion have also been generated using the same computational approach, and their analytical representations have been used for the variational determination of their rovibrational energy levels. Our computations reveal the localization of the additional electron into an anti-bounding molecular orbital associated with the N-Cl bond. The modelling of the photoelectron spectrum of HNCl(-) and DNCl(-) is also presented, showing the vibrational progression associated with the N-Cl stretching mode.