If a maxim passes the contradiction in conception test but fails the contradiction in the will test (fourth step), one has an imperfect duty to pursue a policy admitting of exceptions.
The fourth step of the categorical imperative procedure; failing it generates an imperfect duty.
imperfect duty(Kant's moral philosophy; examples include the duty not to let one's talents rust and the duty not to deny help to others)
A duty that does not specify how, when, or for whom it should be fulfilled; it obligates the adoption of an end rather than a particular action, leaving latitude in its execution
maxim(Kant's formulation of the categorical imperative)
The prescription of an action together with the reason for it
If your maxim fails the third step, you have a “perfect” duty admitting “of no exception in favor of inclination” to refrain from acting on that maxim (G 4:421). If your maxim fails the fourth step, you have an “imperfect” duty requiring you to pursue a policy that can admit of such exceptions. If your maxim passes all four steps, only then is acting on it morally permissible. Following Hill (1971), we can understand the difference in duties as formal: Perfect duties come in the form “One must n