InOpen-shell molecules thisRelativistic coupled-cluster theory article, we provide a brief account of various four-component relativistic single-reference coupled-cluster (SRCC) methods useful in the search for \(\mathcal {P,T}\) -violating effects, particularly the electron electric dipole momentElectron Electric Dipole Moment (eEDM) (eEDM), the nuclear magnetic quadrupole momentNuclear Magnetic Quadrupole Moment (MQM), and the scalar-pseudoscalarScalar-pseudoscalar nucleon-electron interaction nucleon-electron neutral current interaction in open-shell moleculesOpen-shell molecules. Recent applications of these methods in the accurate prediction of the \(\mathcal {P,T}\) -violating sensitivity parameters in promising diatomic and polyatomic molecules are also discussed, along with a brief overview of experimental searches for the eEDMElectron Electric Dipole Moment (eEDM) using polar paramagnetic molecules. The relativistic SRCC methods have emerged as efficient and reliable tools for guiding and supporting high-precision molecular experiments aimed at detecting new sources of \(\mathcal {P,T}\) -odd interactions by providing the molecular sensitivity parameters for the respective interactions.