Density functional theory (DFT) is a key tool for studying the defect chemistry of functional materials. Previous defect studies have primarily focused on understanding the effects of lithium and oxygen vacancies on the P 4 3 32 and F d3m LMNO with various Mn/Ni orderings using a 56-atom supercell. Although they have provided useful insights on defect formation and cation disorder, these studies have various deficiencies: (i) ignoring the effect of atomic chemical potentials on the defect formation energies; (ii) neglecting to address the spurious long-range Coulomb interactions between charged defects inherent within the supercell approach; (iii) calculating defect properties within a small supercell corresponding to unrealistically large defect concentrations. In this paper, we present a comprehensive study of the energetics and behaviour of intrinsic defects in P 4 3 32 LMNO. We first systematically study the magnetic ordering in bulk LMNO, before computing bulk properties and all stable competing phases in the Li-Mn-Ni-O chemical space to determine the phase stability region. We then calculate all intrinsic defects in all possible charge states, using Bader charges, charge densities and Madelung site potential analysis to characterise charge compensation mechanisms and identify small polaron formation. We also investigate a range of likely defect complexes and the migration of lithium defects. Finally, we discuss the effect of synthesis conditions on defect chemistry and how this can explain experimental observations and guide defect-controlled synthesis.