The Landau theory of charge density wave states in 2H-TaSe₂ is re-examined in the light of the commensurate superlattice structure determination by Bird, McKernan and Steeds (1985). It is shown that interlayer interactions play a far more important role in determining the phasing of the CDW/PSD than has been previously assumed. Some consequences of this for the nature of incommensurate states and the interpretation of previous experimental data are also discussed.