Disclosed is a process for the coproduction of acetic acid and acetic anhydride by producing in a first carbonylation reactor a carbonylation product mixture containing acetic anhydride, removing the carbonylation mixture from the first carbonylation reactor, contacting the carbonylation mixture with methanol to react with and convert some or all of the acetic anhydride contained in the mixture to acetic acid and methyl acetate, feeding the resulting reaction composition to a second carbonylation reactor and contacting the reaction composition to carbonylation.