A numerical model of the Hebrides shelf edge (represented by a cross section) is used to examine the non-linear interactions producing energy at the fM2 frequency. Calculations show that in the near coastal ocean this is primarily due to coupling between wind induced inertial oscillations (although near inertial internal waves are present) and the M2 internal tide. The major non-linear interaction, and hence largest fM2 currents, occurs in the region of the thermocline and is associated with shear in the inertial oscillation and the vertical velocity due to the internal tide. This non-linear process represents an important contribution to the energy cascade from the wind and tide into higher frequency waves and eventually mixing. The fM2 current is shown to be a maximum in the shelf edge region and hence measurements in this area will be particularly valuable in determining the extent to which models can represent non-linear processes.