A process for producing acetic acid comprising: a) contacting methanol and carbon monoxide in the presence of a reaction medium under carbonylation conditions sufficient to form acetic acid, wherein the reaction medium comprises: i) a carbonylation catalyst selected from rhodium catalysts, iridium catalysts and palladium catalysts; ii) from 1 wt.% to 14 wt.% water; and iii) a plurality of additives, in-situ generated derivatives of the plurality of additives or combinations thereof; 1) wherein the plurality of additives comprise a first additive and a second additive; 2) wherein the first additive comprises one or more phosphine oxides selected from bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (BAPO), (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (TMDPO), tri-butyl phosphine oxide (TBPO), tri-phenyl phosphine oxide (TPPO) and combinations thereof; and 3) the second additive is selected from heteropolyacids, metal salts and combinations thereof, wherein the heteropolyacids are selected from 12-tungstophosphoric acid, 12-tungstosilicic acid, 12-molybdophosphoric acid, 12-molybdosilicic acid and combinations thereof-the metal salt is selected from zinc acetate (ZnOAc), chromium tri chloride (CrCl 3), chromium acetate hydroxide (CrOAcOH), lanthanide acetate (LaOAc), zirconium hydroxide (ZrOH), yttrium acetate (YOAc) and combinations thereof; and b) recovering acetic acid from the process. a) contacting methanol and carbon monoxide in the presence of a reaction medium under carbonylation conditions sufficient to form acetic acid, wherein the reaction medium comprises: i) a carbonylation catalyst selected from rhodium catalysts, iridium catalysts and palladium catalysts; ii) from 1 wt.% to 14 wt.% water; and iii) a plurality of additives, in-situ generated derivatives of the plurality of additives or combinations thereof; 1) wherein the plurality of additives comprise a first additive and a second additive; 2) wherein the first additive comprises one or more phosphine oxides selected from bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (BAPO), (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (TMDPO), tri-butyl phosphine oxide (TBPO), tri-phenyl phosphine oxide (TPPO) and combinations thereof; and 3) the second additive is selected from heteropolyacids, metal salts and combinations thereof, wherein the heteropolyacids are selected from 12-tungstophosphoric acid, 12-tungstosilicic acid, 12-molybdophosphoric acid, 12-molybdosilicic acid and combinations thereof-the metal salt is selected from zinc acetate (ZnOAc), chromium tri chloride (CrCl 3), chromium acetate hydroxide (CrOAcOH), lanthanide acetate (LaOAc), zirconium hydroxide (ZrOH), yttrium acetate (YOAc) and combinations thereof; and i) a carbonylation catalyst selected from rhodium catalysts, iridium catalysts and palladium catalysts; ii) from 1 wt.% to 14 wt.% water; and iii) a plurality of additives, in-situ generated derivatives of the plurality of additives or combinations thereof; 1) wherein the plurality of additives comprise a first additive and a second additive; 2) wherein the first additive comprises one or more phosphine oxides selected from bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (BAPO), (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (TMDPO), tri-butyl phosphine oxide (TBPO), tri-phenyl phosphine oxide (TPPO) and combinations thereof; and 3) the second additive is selected from heteropolyacids, metal salts and combinations thereof, wherein the heteropolyacids are selected from 12-tungstophosphoric acid, 12-tungstosilicic acid, 12-molybdophosphoric acid, 12-molybdosilicic acid and combinations thereof-the metal salt is selected from zinc acetate (ZnOAc), chromium tri chloride (CrCl 3), chromium acetate hydroxide (CrOAcOH), lanthanide acetate (LaOAc), zirconium hydroxide (ZrOH), yttrium acetate (YOAc) and combinations thereof; and 1) wherein the plurality of additives comprise a first additive and a second additive; 2) wherein the first additive comprises one or more phosphine oxides selected from bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (BAPO), (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide (TMDPO), tri-butyl phosphine oxide (TBPO), tri-phenyl phosphine oxide (TPPO) and combinations thereof; and 3) the second additive is selected from heteropolyacids, metal salts and combinations thereof, wherein the heteropolyacids are selected from 12-tungstophosphoric acid, 12-tungstosilicic acid, 12-molybdophosphoric acid, 12-molybdosilicic acid and combinations thereof-the metal salt is selected from zinc acetate (ZnOAc), chromium tri chloride (CrCl 3), chromium acetate hydroxide (CrOAcOH), lanthanide acetate (LaOAc), zirconium hydroxide (ZrOH), yttrium acetate (YOAc) and combinations thereof; and b) recovering acetic acid from the process.