Work done in moving a charge through an electric field

In electrostatics, when you apply an external force to a charge in an electric field to move it from A to B against the field, why is the force said to be equal to the force the electric field is exerting on the charge? How come we're allowed to neglect the initial slightly greater force needed to accelerate the charge?

This comes from my text supposing that an external force moves a charge through the field without changing it's kinetic energy..