A process for the manufacture of dialkyl phosphites is disclosed. In detail, dialkyl phosphites are prepared starting from P4O6, or partially hydrated species thereof cumulatively P—O, by reacting specific molar ratios of alcohol and P—O, containing from 1 to 6 P—O—P bonds in the molecule, in the presence of trialkylphospite (TAP) to thus yield high purity and high yield of dialkyl phosphites. The P—O reactant is preferably represented by liquid P4O6.