| 5020 | Inspection service, automotive | |
| 7523 | Inspection service, fishery | |
| 4540 | Installation contractors of ornamental or architectural shapes | |
| 4530 | Installation of diffusers, grilles, air registers | |
| 4530 | Installation of glass fibre or mineral wool materials | |
| 4530 | Installation of heavy equipment | |
| 4520 | Installation of interlocking stone, driveways | |
| 4530 | Installation of machinery and other industrial equipment, contractors | |
| 4530 | Installation of polystyrene or other foamed "board" or "panel" materials | |
| 4540 | Installation of storm doors, metal | |
| 4540 | Installation of window panes | |
| 4540 | Installation of windows, metal | |
| 4540 | Installation of windows, wooden | |
| 9214 | Installing and dismantling concert stages, sound and lighting equipment, on a contract basis | |
| 6592 | Installment sales finance company | |
| 1531 | Instant cereal beverage, manufacturing | |
| 1549 | Instant coffee, manufacturing | |
| 1531 | Instant hot cereals, manufacturing | |
| 2221 | Instant printing (i.e., quick printing) | |
| 1549 | Instant tea, manufacturing | |
| 8030 | Institute of marine technology, post-secondary | |
| 8030 | Institutes of technology (non-university) | |
| 4520 | Institutional buildings, construction | |
| 3150 | Institutional lighting fixtures, manufacturing | |
| 7523 | Institutions, correctional, federal government | |
| 7523 | Institutions, correctional, provincial | |
| 9211 | Instructional film production | |
| 9211 | Instructional video production | |
| 1912 | Instrument cases, all materials, manufacturing | |
| 3190 | Instrument control panels (i.e., assembling purchased gauges), automotive, truck and bus, manufacturing | |
| 3312 | Instrument landing system instrumentation, airborne or airport, manufacturing | |
| 3320 | Instrument lenses, manufacturing | |
| 3312 | Instrument panels, assembling using gauges made in the same establishment | |
| 3120 | Instrument relays, all types, manufacturing | |
| 3312 | Instrument shunts, manufacturing | |
| 2899 | Instrument springs, precision (except clock and watch), manufacturing | |
| 3110 | Instrument transformers (except portable), manufacturing | |
| 3110 | Instrument transformers, electronic, manufacturing | |
| 3312 | Instrumentation for reactor controls, auxiliary, manufacturing | |
| 3311 | Instruments and apparatus, medical, surgical, ophthalmic, and veterinary | |