Despite resolving a rich set of molecular and bioelectronic phenomena such as charge transport, polarization, dielectric effects, and interfacial dynamics, EIS suffers from ambiguity and lack of identifiability that allows the assignment of any arbitrary circuit to molecular impedance characteristics. In this work we introduce a relaxation-time atlas with identifiability criteria and uncertainty quantification procedures for discerning molecular effects from contact resistance, pad and fringe capacitance, ionic screening, dipolar polarization, geometry effects, instrument response, and other non-molecular parasitic effects that could swamp the intrinsic molecular behavior. Our atlas uses a physically explicit impedance decomposition, frequency scaling tests specific to a mechanism, Kramers–Kronig consistency, identifiability checks, and rules for uncertainty quantification. The credibility of each assigned molecular impedance parameter is quantified in the form of a Molecular Impedance Credibility Index (MICI). Rather than taking an equivalent circuit label as evidence of molecular behavior, MICI provides a measure of support for the assignment of each component and its value to molecular effects. We develop the validation logic specifically for self-assembled monolayer tunnel junctions, molecular wire junctions, ion-containing devices, solvent sensitive devices, protein junctions, mesoscopic quantum RC circuits, and atomic contacts. The proposed methodology thus represents a protocol for consistent analysis of molecular junction impedances based on geometric, frequency response, temperature, and voltage conditions as well as environmental manipulations, parasitic corrections, and uncertainty quantification procedures.