| 7421 | Acoustical engineering consulting services | |
| 4540 | Acoustical foam, sound barrier, installation | |
| 4540 | Acoustical service contractor | |
| 4540 | Acoustical services for buildings | |
| 2811 | Acoustical suspension systems, metal, manufacturing | |
| 7421 | Acoustical system design services, engineering | |
| 4540 | Acoustical tile and panels contractor | |
| 7493 | Acoustical tile cleaning service | |
| 4540 | Acoustical wall panels, installation | |
| 7422 | Acoustics testing services | |
| 9211 | Acquiring and reselling distribution rights to movies and videos | |
| 2411 | Acrolein, manufacturing | |
| 2413 | Acrylate rubber, manufacturing | |
| 2413 | Acrylate-butadiene rubber, manufacturing | |
| 1711 | Acrylic and modacrylic filament yarn, throwing, twisting, texturizing or winding purchased yarn | |
| 2430 | Acrylic fibres and filaments, manufacturing | |
| 2520 | Acrylic film and unlaminated sheet, manufacturing | |
| 2413 | Acrylic resins, manufacturing | |
| 2413 | Acrylic rubber, manufacturing | |
| 1711 | Acrylic spun yarns, made from purchased fibre | |
| 2430 | Acrylonitrile fibres and filaments, manufacturing | |
| 2411 | Acrylonitrile, manufacturing | |
| 2413 | Acrylonitrile-butadiene-styrene (ABS) resins, manufacturing | |
| 1429 | Actinolite mine | |
| 3312 | Actinometers, meteorological, manufacturing | |
| 3694 | Action figures (toys), manufacturing | |
| 2429 | Activated carbon and charcoal, manufacturing | |
| 2429 | Activated clays, earths and other mineral products, manufacturing | |
| 8532 | Activity centres, elderly or handicapped | |
| 9214 | Actors, independent | |
| 9214 | Actresses, independent | |
| 6720 | Actuarial consulting services | |
| 2912 | Actuators, fluid power, manufacturing | |
| 8519 | Acupuncturists (except M.D.), offices of | |
| 8519 | Acupuncturists' offices | |
| 2411 | Acyclic hydrocarbons (except acetylene), made from refined petroleum or natural gas liquids | |
| 2927 | Adapters, bombcluster, manufacturing | |
| 8511 | Addiction hospitals | |
| 7123 | Adding machine rental | |
| 3000 | Adding machines (except electronic), manufacturing | |