When a block is stationary on an inclined plane, the frictional force on the base of the block has a torque about the center of gravity of the block. However, the block does not rotate. Which force provides the opposing torque to that of friction? This opposing torque cannot be from gravity, since both components of the gravitational force on the block (parallel and perpendicular to the plane) pass through the center of gravity of the block and have no torque about it. Where does the opposing torque come from in order to keep the block from rotating?
The torque due to friction here is balanced by torque due to normal reaction because the point of action of normal reaction changes.It changes due to torque due to friction, which tilts the block a little and the normal reaction does not act along the center of gravity
The block looses some points of contact and thus normal reaction shifts downwards due to toppling effect of friction which inturn balances the torque due to friction.