method in the open-source Psi4 package. In this work, we make use of the t 1 -transformed Hamiltonian to reduce the complexity of the CCSD equations, and we present our own set of LCCSD working equations that minimize common sources of error in PNO-based methods, like PNO projection error. We have also developed a set of parameters that allow our code to yield relative energies with deviations on the order of 0.1 kcal mol -1 from canonical CCSD(T), called TightPNO, following the convention of Neese et al. We test our code extensively on relative energies, including interaction energies and conformation energies. Weak, non-covalent interactions have historically been a challenge for local correlation methods. We also present results