| 58 Degrees North Ltd | Arts & recreation | 2020 |
| 58 Nørth Ltd | Manufacturing | 2025 |
| A & J Mackay Plumbing & Heating Ltd | Construction | 2008 |
| A & R Shellfish Ltd | Agriculture & fishing | 2014 |
| A Sutherland Ltd | Construction | 2022 |
| A&W Sinclair Ltd | Construction | 2005 |
| A. & D. Sutherland Limited | Mining & quarrying | 1954 |
| A.Brm Property Ltd | Real estate | 2025 |
| A.R.W Wilson Limited | Transport & logistics | 2025 |
| AAM Haulage Ltd | Transport & logistics | 2015 |
| Above and Beyond Tours Caithness Ltd | Administrative & support | 2025 |
| Acc+Ess Limited | Manufacturing | 2011 |
| Acme Plant Hire Ltd | Construction | 2019 |
| Active Animals Rescue and Rehabilitation Ltd | Professional & scientific | 2019 |
| Agriflight Solutions Ltd | Agriculture & fishing | 2025 |
| Agung Sauna Limited | Other services | 2025 |
| Albyn Consulting Services Ltd | Professional & scientific | 2025 |
| Allan's of Gillock Limited | Wholesale & retail | 1986 |
| Alpha Health Physics Limited | Professional & scientific | 2018 |
| Alvry Ltd | Real estate | 2022 |
| Alyson Ltd | Agriculture & fishing | 2019 |
| AMC Offshore Ltd | Professional & scientific | 2025 |
| Anderholm Properties Ltd | Real estate | 2024 |
| Andrew K Gunn Limited | Construction | 2008 |
| Andrew Robertson (Wick) Ltd | Construction | 2005 |
| Andron Partners Ltd | Agriculture & fishing | 2012 |
| Angels Share Competitions Ltd | Other services | 2024 |
| Annapurna Hospitality Limited | Hospitality | 2026 |
| Annie's Bakery Limited | Manufacturing | 2013 |
| Arca Ross Ltd | Professional & scientific | 2026 |
| Ashley ANN Limited | Manufacturing | 1986 |
| ASM Spice Wick Ltd | Hospitality | 2023 |
| AWB Property Management Ltd | Real estate | 2021 |
| AWS Renewables Ltd | Extraterritorial | 2008 |
| Azrum Ltd | Energy | 2022 |
| B G a Quality Butchers Ltd | Manufacturing | 2014 |
| B&S North Coast Properties Ltd | Real estate | 2025 |
| Bald Bear Ltd | Professional & scientific | 2025 |
| Baseline Research Limited | Professional & scientific | 2006 |
| BBM Solicitors Limited | Professional & scientific | 2015 |
| Bdoptimal Ltd | Transport & logistics | 2025 |
| Best Wishes (Wick) Limited | Wholesale & retail | 2016 |
| BGM Quality Services Ltd | Mining & quarrying | 2014 |
| Bilbster Ltd | Agriculture & fishing | 2025 |
| Biomac Limited | Energy | 2017 |
| Black Stairs House Ltd | Wholesale & retail | 2026 |
| Blackstairs Kilts Ltd | Wholesale & retail | 2025 |
| Booth Letting Services Ltd | Real estate | 2025 |
| Bramley Landscapes Ltd | Administrative & support | 2018 |
| Bremco Engineering Ltd | Construction | 2021 |
| Bremner Fishing Company Limited | Agriculture & fishing | 1983 |
| Brewington Capability Development Ltd | Professional & scientific | 2023 |
| Bridge Spice Ltd | Hospitality | 2023 |
| Bridgnorth Ironmongers Limited | Wholesale & retail | 2011 |
| Broadhaven Fishing Company Ltd | Agriculture & fishing | 2014 |
| Build With Zero Ltd | Information & communication | 2024 |
| C a LEE Ltd | Administrative & support | 2017 |
| C H Carter Ltd | Construction | 2024 |
| C M B Macleod Electrical Services Ltd | Professional & scientific | 2012 |
| C&L House Limited | Hospitality | 2026 |
| C.W.O. Limited | Construction | 2009 |
| CAB Roofing Supplies (Marley) Ltd | Extraterritorial | 2024 |
| Caherush Enterprises Limited | Manufacturing | 2024 |
| Caithness BBQ Limited | Hospitality | 2022 |
| Caithness Bouncy Castles Ltd | Arts & recreation | 2023 |
| Caithness Car Club Limited | Arts & recreation | 1984 |
| Caithness Chemicals (Wick) Limited | Manufacturing | 2012 |
| Caithness Chemicals Limited | Agriculture & fishing | 1989 |
| Caithness Contractors Limited | Construction | 2017 |
| Caithness Electronics Limited | Professional & scientific | 2018 |
| Caithness Engineering Services Limited | Professional & scientific | 2017 |
| Caithness Homes Management Company Ltd | Real estate | 2026 |
| Caithness Household Ltd | Wholesale & retail | 2021 |
| Caithness Installations and Furniture Ltd | Construction | 2024 |
| Caithness Luxury Apartments NC500 Ltd | Hospitality | 2022 |
| Caithness Mental Health Support Group | Health & social care | 1992 |
| Caithness Performance Ltd | Wholesale & retail | 2019 |
| Caithness Polyrooms Ltd | Construction | 2024 |
| Caithness Properties Ltd | Hospitality | 2025 |
| Caithness Remaps Ltd | Wholesale & retail | 2023 |
| Caithness Voluntary Group | Health & social care | 1994 |
| Caithness Windows Limited | Administrative & support | 2025 |
| Caithness,Car and Commercial Ltd | Wholesale & retail | 2017 |
| Calder & Barnes Ltd | Construction | 2022 |
| Carrick Farm (Eday) LLP | | 2022 |
| Cash Point Auctions Ltd | Wholesale & retail | 2016 |
| Castle View Stables Ltd | Arts & recreation | 2024 |
| Ceres BIO Ltd | Professional & scientific | 2021 |
| Chan EIL Ltd | Hospitality | 2025 |
| Cheeky Chimps Park Ltd | Arts & recreation | 2025 |
| Clear Ears North Coast Ltd | Health & social care | 2026 |
| Coast Serviced Apartments Ltd | Hospitality | 2019 |
| Cogle Wood Ltd | Agriculture & fishing | 2014 |
| Cormack Engineering Ltd | Manufacturing | 2024 |
| County Joiners Limited | Construction | 2007 |
| Craigallan Services Limited | Mining & quarrying | 2018 |
| Crawford & Coghill Homes Limited | Real estate | 2024 |
| Curl UP 'N' DYE (Wick) Ltd | Other services | 2010 |
| CWS Road Freight Ltd | Transport & logistics | 2025 |
| D Coghill & SON Joiners (Wick) Ltd | Construction | 2016 |