Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculations have been performed to evaluate three-bond 15N−31P coupling constants (3hJN-P) across N−H···O−P hydrogen bonds in model cationic and anionic complexes including NH4+:OPH, NH4+:OPH3, NH3:-O2PH2, NFH2:-O2PH2, and NF2H:-O2PH2. Three-bond coupling constants can be appreciable when the phosphorus is P(V), but are negligible with P(III). 3hJN-P values in complexes with cyclic or open structures are less than 1 Hz, a consequence of the nonlinear arrangement of N, H, O, and P atoms. For complexes with these structures, 3hJN-P may not be experimentally measurable. In contrast, complexes in which the N, H, O, and P atoms are collinear or nearly collinear have larger values of 3hJN-P , even though the N−P distances are longer than N−P distances in cyclic and open structures. In linear complexes, 3hJN-P is dominated by the Fermi-contact term, which is distance dependent. Therefore, N−P (and hydrogen-bonding N−O) distances in these complexes can be determined from experimentally measured 15N−31P coupling constants.