This report describes the inverse electro- and magnetostatic modelling program Inesma V2.1. The inverse problem is formulated as a non-linear least squares problem that is solved with a constrained quasi-Newton like method. The static electric or the static magnetic field is modelled with either monopoles or dipoles in a horizontally stratified threelayer model consisting of air, water and seabed. The reference field is generated from a synthetic model or read from file. the output from Inesma is a source distribution that locally minimises the costfunction. Worked examples are given for a synthetic electric and a synthetic magnetic signature.