We show that ambiguities and symmetry violations arising in one loop calculations can always be avoided provided the regularization scheme employed satisfies three consistency conditions. Our calculations are effected by assuming only implicitly the presence of a regulator in the integrand. We demonstrate in this way that there is a set of three relations involving divergent integrals of the same degree of divergence which are the source of both ambiguities and symmetry violations in Quantum Electrodynamics. Moreover we give analytical expressions for the finite parts of amplitudes off the mass shell systematized in terms of a set of special functions. Ward identities require hightly nom trivial relations involving those functions which we also derive.