Nonunitary mixing: current constraints and new ambiguity

Neutrino physics has been under continuos progress along several decades from now. As a consequence, the main parameters for neutrino mixing are under constant improvement and entering into a precision era that will allow testing for the unitarity of the mixing matrix in the leptonic sector. Here we discuss the triangular parametrization as a useful tool in this context, and we give a brief discussion on the current status on the restriction to its parameters.