A method of reducing acetaldehyde production in a polyester, the method comprising: (a) selecting an acetaldehyde scavenger which includes an amine moiety, an amide moiety and a substituted phenyl moiety; (b) selecting a phosphorus additive, being an additive comprising a phosphorus moiety; and (c) contacting the polyester which has an IV of greater than 0.5 dL/g (determined according to the method of the description) with said acetaldehyde scavenger and with said phosphorus additive, wherein: (i) in step (c), polyester is contacted with at least 5ppm and less than 1000ppm of acetaldehyde scavenger per part of polyester; and is contacted with at least 15ppm and less than 500ppm of phosphorus additive per part of polyester; and/or (ii) the ratio of the ppm of a said selected acetaldehyde scavenger to the ppm of a said selected phosphorus additive is in the range 0.5 to 25; and/or (iii) the ratio of the ppm of a said selected acetaldehyde scavenger to the ppm of a said selected phosphorus additive is in the range 1 to 5000; and/or (iv) a mixture comprising said acetaldehyde scavenger, said phosphorus additive and a polyester compatible organic liquid carrier is selected prior to step (c) and the mixture is contacted with the polyester in step (c). (a) selecting an acetaldehyde scavenger which includes an amine moiety, an amide moiety and a substituted phenyl moiety; (b) selecting a phosphorus additive, being an additive comprising a phosphorus moiety; and (c) contacting the polyester which has an IV of greater than 0.5 dL/g (determined according to the method of the description) with said acetaldehyde scavenger and with said phosphorus additive, wherein: (i) in step (c), polyester is contacted with at least 5ppm and less than 1000ppm of acetaldehyde scavenger per part of polyester; and is contacted with at least 15ppm and less than 500ppm of phosphorus additive per part of polyester; and/or (ii) the ratio of the ppm of a said selected acetaldehyde scavenger to the ppm of a said selected phosphorus additive is in the range 0.5 to 25; and/or (iii) the ratio of the ppm of a said selected acetaldehyde scavenger to the ppm of a said selected phosphorus additive is in the range 1 to 5000; and/or (iv) a mixture comprising said acetaldehyde scavenger, said phosphorus additive and a polyester compatible organic liquid carrier is selected prior to step (c) and the mixture is contacted with the polyester in step (c). (i) in step (c), polyester is contacted with at least 5ppm and less than 1000ppm of acetaldehyde scavenger per part of polyester; and is contacted with at least 15ppm and less than 500ppm of phosphorus additive per part of polyester; and/or (ii) the ratio of the ppm of a said selected acetaldehyde scavenger to the ppm of a said selected phosphorus additive is in the range 0.5 to 25; and/or (iii) the ratio of the ppm of a said selected acetaldehyde scavenger to the ppm of a said selected phosphorus additive is in the range 1 to 5000; and/or (iv) a mixture comprising said acetaldehyde scavenger, said phosphorus additive and a polyester compatible organic liquid carrier is selected prior to step (c) and the mixture is contacted with the polyester in step (c).