| 31913 | Oars, wooden | |
| 23140 | Oats, clipped, whether or not pearled | |
| 23140 | Oats, hulled, whether or not sliced or kibbled | |
| 23140 | Oats, kibbled | |
| 23140 | Oats, pearled | |
| 23140 | Oats, roasted or swollen as breakfast food, ready for consumption | |
| 23140 | Oats, rolled or flaked (excl. prepared breakfast foods) | |
| 01171 | Oats, seed | |
| 01172 | Oats, unmilled | |
| 48311 | Objectives (incl. polarizing) for astronomical instruments, binoculars, refracting telescopes, microscopes | |
| 89330 | Objects, metal, manufacturing of, by pressure | |
| 89330 | Objects, metal, manufacturing of, by sintering | |
| 89330 | Objects, metal, manufacturing of, from metal powders | |
| 85340 | Objects, sterilizing of | |
| 38330 | Oboes | |
| 37990 | Obsidian, expanded or exfoliated | |
| 16310 | Obsidian, precious, unworked or simply sawn or roughly shaped, whether or not graded, not strung, mounted or set | |
| 38220 | Obsidian, precious, worked other than simply sawn or roughly shaped, whether or not graded, not strung, mounted or set | |
| 93122 | Obstetrical consultation services | |
| 93112 | Obstetrical services delivered under the direction of medical doctors | |
| 38330 | Ocarinas | |
| 91133 | Occupation certificates, building, issuing of | |
| 93193 | Occupational therapy services | |
| 14290 | Ochre, bismuth (bismuth ore) | |
| 16190 | Ochres (earth colours), whether or not calcined or mixed together or with other earth colours (excl. bismuth ochre) | |
| 34140 | Oct-1-yne-carboxylic acid | |
| 34110 | Octachloronaphthalene | |
| 34110 | Octachlorotetrahydro-4,7-endomethyleneindane | |
| 34110 | Octachlorotetrahydromethanoindane | |
| 34139 | Octadecan-1-ol | |
| 34110 | Octadecane | |
| 34140 | Octadecyl methacrylate | |
| 34110 | Octafluorocyclobutane | |
| 34160 | Octamethylcyclotetrasiloxane | |
| 34150 | Octamethylpyrophosphoramide (OMPA) | |
| 34160 | Octamethyltrisiloxane | |
| 34139 | Octan-1-ol | |
| 34170 | Octanal | |
| 48269 | Octane index-measuring appliances for laboratories | |
| 34110 | Octanes | |