Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculations have been performed to evaluate three-bond N-15-P-31 coupling constants ((3h)J(N-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). (3h)J(N-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, (3h)J(N-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 (3h)J(N-P), even though the N-P distances are longer than N-P distances in cyclic and open structures. In linear complexes, (3h)J(N-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 N-15-P-31 coupling constants.