We consider the collective model of labor supply with marketable domestic production. We first show that, if domestic production is mistakenly ignored, the 'collective' indirect utility functions that are retrieved from observed behavior will be unbiased if and only if the profit function is additive. Otherwise, in the non-additive case, the direction and the size of the bias will depend on the complementaritysubstitutability of spouses' time inputs in the production process. We then show that, even if domestic labor supply functions are not observed, valid welfare comparisons are possible. This identification result generalizes that in Chiappori (1992).