A process for the hydroformylation of olefins having from 20 to 400 carbon atoms by reaction of the olefins with synthesis gas in the presence of a cobalt carbonyl catalyst and recovery of the cobalt catalyst by extraction of the reaction product with an aqueous acidic solution in the presence of oxygen and separation of the organic and aqueous phases, wherein (a) the aqueous phase is separated from the organic phase by means of gravitational forces to the extent that the proportion of aqueous phase dispersed in the organic phase is 2% by weight or less, based on the organic phase, and (b) the organic phase obtained in step (a) is exposed to an electric field to coalesce the remaining dispersed aqueous phase, is described. In this way, the residual cobalt content of the hydroformylation product can be reduced to less than 1 ppm.