| Carters of Swanwick Limited | Other services | 2009 |
| Cartesian I.T. Consultancy Ltd | Information & communication | 2010 |
| Cartish Limited | Wholesale & retail | 2025 |
| Cartland Commercials Ltd | Wholesale & retail | 2011 |
| Cartland Garage Services Limited | Wholesale & retail | 2011 |
| Cartland Industrial Tyres Ltd | Wholesale & retail | 2015 |
| Cartland Truck Stop Limited | Transport & logistics | 2023 |
| Cartland Vehicle Repairs Limited | Wholesale & retail | 2026 |
| Cartwright CS Ltd | Transport & logistics | 2021 |
| Casa Bodega Limited | Hospitality | 1999 |
| Casa Brasil (Bristol) Limited | Hospitality | 2015 |
| Casa Brasil (Bristol) Trading Limited | Professional & scientific | 2015 |
| Casa Brasil (Holdings) Limited | Financial services | 2015 |
| Casa Brasil (Port Solent Holdings) Limited | Financial services | 2020 |
| Casa Brasil (Port Solent) Limited | Hospitality | 2012 |
| Casa Brasil (West Quay) Limited | Hospitality | 2015 |
| Casa Brasil Ocean Village Limited | Hospitality | 2020 |
| Casa MIA Lettings Ltd | Real estate | 2019 |
| Casa Nostra Properties Ltd | Real estate | 2023 |
| Casata Property Developments Ltd | Construction | 2025 |
| Cascoda Limited | Administrative & support | 2007 |
| Cascontractors Ltd | Construction | 2023 |
| Case Investments (Hampshire) Limited | Real estate | 2017 |
| Casenterprise Limited | Health & social care | 2024 |
| Cashsolv Ltd | Professional & scientific | 2012 |
| Cass Productions Limited | Information & communication | 1998 |
| Cassiobury Residential Management Company Limited | Households | 2008 |
| Cassiopeia Star Finance Limited | Financial services | 2017 |
| Cassiopeia Star Holdings Limited | Financial services | 2017 |
| Cassiopeia Star Investments Limited | Financial services | 2020 |
| Casstar Investments Limited | Real estate | 2021 |
| Casswinn IT Limited | Information & communication | 2019 |
| Castle Angling Club Limited(The) | Arts & recreation | 1979 |
| Castle Bidco Limited | Other services | 2024 |
| Castle Carpentry Contractors (Southampton) Limited | Construction | 1992 |
| Castle Court Investment Company (Southampton) Limited | Real estate | 1959 |
| Castle Heights Management (Southampton) Limited | Households | 1999 |
| Castle Homes Construction Ltd | Construction | 2025 |
| Castle Keep Developments Ltd | Real estate | 2023 |
| Castle Kenwood Plant Limited | Administrative & support | 1999 |
| Castle Lane Car Company Ltd | Wholesale & retail | 2024 |
| Castle Mews Residents Management Company Limited | Households | 2007 |
| Castle Midco 1 Limited | Other services | 2024 |
| Castle Midco 2 Limited | Other services | 2024 |
| Castle Properties Estate Agents Limited | Real estate | 2008 |
| Castle Securities UK Limited | Real estate | 2003 |
| Castle Sunbury Limited | Real estate | 2018 |
| Castle Topco Limited | Other services | 2024 |
| Castle Tyres Ltd | Wholesale & retail | 2020 |
| CASTLE4CARS Limited | Wholesale & retail | 2012 |
| Castlegate Windows Limited | Wholesale & retail | 1999 |
| Castlehaven Limited | Agriculture & fishing | 2003 |
| Castlemain Groundworks Ltd | Construction | 2018 |
| Castlemaine Fiduciary Services Limited | Professional & scientific | 2014 |
| Castleway Cooling Limited | Construction | 2011 |
| Castleway Limited | Construction | 1994 |
| Castra Services Limited | Other services | 2015 |
| Castro Transport Ltd | Transport & logistics | 2023 |
| Castrum Limited | Information & communication | 2000 |
| Catalin Logistic Ltd | Transport & logistics | 2021 |
| Catalyst Design & Marketing Ltd | Professional & scientific | 2008 |
| Catalyst Finance Limited | Financial services | 2022 |
| Catalyst Personal Training Ltd | Arts & recreation | 2009 |
| Catav Ltd | Transport & logistics | 2024 |
| Catchmate Ltd | Information & communication | 2026 |
| Cater Building Repairs Limited | Real estate | 2017 |
| Cater Engineers Limited | Construction | 2018 |
| Caterange Limited | | 1978 |
| Catermasters Contract Catering (Holding) Company Limited | Hospitality | 2012 |
| Catermasters Contract Catering Limited | Hospitality | 1999 |
| Cathedral City Windows Limited | Construction | 2014 |
| Cathedral Views Limited | Households | 1996 |
| Catherine Alexander DGA Ltd | Professional & scientific | 2021 |
| Catherine Carter Consultancy Limited | Professional & scientific | 2015 |
| Cathie Solutions Limited | Professional & scientific | 2025 |
| Cato Legal Services Limited | Professional & scientific | 2011 |
| Cato Trans Ltd | Transport & logistics | 2015 |
| Catteya Ltd | Hospitality | 2021 |
| Cattrall Financial Solutions Ltd | Financial services | 2010 |
| Catts Contractors Ltd | Administrative & support | 2023 |
| Catty Shack Ltd | Wholesale & retail | 2019 |
| CAV Aircraft Services Ltd | Manufacturing | 2013 |
| Cavalry Logistics Solutions Limited | Transport & logistics | 2023 |
| Cave Enerjie Group Ltd | Manufacturing | 2024 |
| Cave Itsm Consulting Limited | Information & communication | 2023 |
| Cavendish Developments (Southern) Limited | Real estate | 1979 |
| Cavendish Home Lettings Ltd | Real estate | 2016 |
| Cavendish Real Estate Limited | Real estate | 1998 |
| Cavendish Southern Ltd | Extraterritorial | 2009 |
| Cavetto Construction Hampshire Limited | Construction | 2013 |
| CAW Mortgages Limited | Financial services | 2017 |
| CAW Wellbeing CIC | Other services | 2024 |
| Cawte Garage Ltd | Wholesale & retail | 2025 |
| Cawte Road (Southampton) Limited | Professional & scientific | 2007 |
| Cawtes Reach Estate Management Limited | Households | 2010 |
| Caxton Court (Freehold) Limited | Households | 2005 |
| Cay-Ba Ltd | Hospitality | 2024 |
| Cazen Limited | Manufacturing | 2023 |
| CB Media Group Ltd | Administrative & support | 2010 |
| Cbcg Services Limited | Transport & logistics | 2018 |