| Collect & Clean Ltd | Other services | 2024 |
| Collect & Store Limited | Administrative & support | 2016 |
| Collective Catering Limited | Hospitality | 2025 |
| College Chambers Barristers Southampton Ltd | Administrative & support | 2016 |
| Collicutt Limited | Manufacturing | 2019 |
| Collier Capital Limited | Professional & scientific | 2023 |
| Collier Capital Newco 1 Limited | Professional & scientific | 2020 |
| Collingwood Communal Area Limited | Households | 2011 |
| Collingwood Investment Properties Ltd | Construction | 2006 |
| Collingwood Investments Limited | Real estate | 1999 |
| Collins Corporate Solutions Limited | Administrative & support | 2011 |
| Collins Marine Consultants Ltd | Professional & scientific | 2012 |
| Collis Moss Flooring Ltd | Construction | 2024 |
| Collyer Holdings Limited | Financial services | 2020 |
| Colmer Fabs Limited | Manufacturing | 2015 |
| Colocare Limited | Health & social care | 2015 |
| Colonial Furniture Ltd | Wholesale & retail | 2026 |
| Colorivita Ukeig | | 2017 |
| Colosseum Terrace Management Limited | Households | 1996 |
| Colourcat Limited | Wholesale & retail | 2026 |
| Colva Ltd | Information & communication | 2012 |
| Colva Tech Ltd | Information & communication | 2018 |
| Colvill Banks Limited | Administrative & support | 2007 |
| COM & TEL (UK) Ltd | Administrative & support | 1998 |
| COM & TEL Media Limited | Administrative & support | 2019 |
| COM4BUSS Ltd | Wholesale & retail | 2020 |
| Combe Down Residents Association Limited | Households | 1986 |
| Combi-Nation Commercial Ltd | Other services | 2011 |
| Combined Cloud Accounting Limited | Professional & scientific | 2019 |
| Combisteel UK Ltd | Wholesale & retail | 2008 |
| Comcap 10 Limited | Construction | 2015 |
| Cometa 2019 Ltd | Transport & logistics | 2019 |
| Comfort Healthcare Services UK Ltd | Administrative & support | 2013 |
| Comfort Living Homes Ltd | Health & social care | 2023 |
| Cominvest Systems (UK) Limited | Financial services | 1984 |
| Comley Court Management Company Limited | Households | 2003 |
| Command View Ltd | Professional & scientific | 2024 |
| Commbase Ltd | Administrative & support | 2015 |
| Commence Care Limited | Health & social care | 2025 |
| Commerce Enterprises Ltd | Wholesale & retail | 2024 |
| Commercecall Limited | Information & communication | 2019 |
| Commercial and Domestic Cleaning Solutions Made Simple Ltd | Administrative & support | 2025 |
| Commercial Cladding & Building Ltd | Construction | 2024 |
| Commercial Engineering Solutions Ltd | Professional & scientific | 2025 |
| Commercial Glazing Solutions Limited | Construction | 2017 |
| Commercial Intelligence Ltd | Information & communication | 2003 |
| Commercial Laundry & Electrical Services Limited | Manufacturing | 2021 |
| Commercial Laundry Equipment Services Limited | Manufacturing | 2005 |
| Commercial Refurbishment Services Limited | Real estate | 1998 |
| Commercial Road Restaurant Limited | Hospitality | 2023 |
| Commodore Court Management Company Limited | Households | 1992 |
| Common Barn Ltd | Wholesale & retail | 2010 |
| Communibakes Ltd | Wholesale & retail | 2021 |
| Communicare in Southampton | Health & social care | 2005 |
| Communication Cellular Services Ltd | Information & communication | 2012 |
| Community Hatch Limited | Other services | 2023 |
| Community Infrastructure Group CIC | Professional & scientific | 2015 |
| Comniti Housing CIC | Hospitality | 2025 |
| COMP-U-2000 Limited | Information & communication | 1996 |
| Compact Property Services Ltd | Administrative & support | 2003 |
| Companion Hands Ltd | Health & social care | 2025 |
| Company Management Resources Limited | Professional & scientific | 2019 |
| Company of Proprietors of Whitchurch Bridge (the) | Transport & logistics | 1981 |
| Company X Limited | Real estate | 1976 |
| Comparison Technologies Limited | Financial services | 2017 |
| Comparison Technologies Service Hub Limited | Financial services | 2007 |
| Compass Boat Sales Ltd | Wholesale & retail | 2024 |
| Compass Brickwork Limited | Construction | 2018 |
| Compass Clinic Limited | Health & social care | 2009 |
| Compass Court (Southampton) RTM Company Ltd | Households | 2017 |
| Compass Land Ltd | Real estate | 2016 |
| Compass Paving Limited | Wholesale & retail | 1999 |
| Compass Personal Finance Ltd | Financial services | 2021 |
| Competent Healthcare Ltd | Health & social care | 2017 |
| Competition Sport Recycling Ltd | Wholesale & retail | 2024 |
| Competition Sport Retrofits Ltd | Wholesale & retail | 2025 |
| Complementary Medical Centre Ltd | Health & social care | 2011 |
| Complete Book Ltd | Professional & scientific | 2026 |
| Complete Business Opportunities Ltd. | Administrative & support | 2012 |
| Complete Cash Management Ltd | Administrative & support | 2012 |
| Complete Coaching Ltd | Education | 2026 |
| Complete Coatings Consultancy Limited | Professional & scientific | 2015 |
| Complete Event Solutions Ltd | Administrative & support | 2003 |
| Complete FS Limited | Financial services | 2012 |
| Complete Gardening & Fencing Services Ltd | Administrative & support | 2021 |
| Complete Law LLP | | 2006 |
| Complete Limited | Extraterritorial | 2015 |
| Complete Refurbishment and Development Ltd. | Construction | 2013 |
| Complete Rigging Solutions Ltd | Construction | 2023 |
| Complete Security (Southern) Limited | Administrative & support | 2015 |
| Complete Solutions CS UK Ltd | Construction | 2017 |
| Completely Gorgeous Beauty Limited | Other services | 2016 |
| Complycare Plus Limited | Information & communication | 2025 |
| Composite Consultancy Ltd | Professional & scientific | 2021 |
| Composite Rigging Limited | Extraterritorial | 1998 |
| Composite Specialities Limited | Manufacturing | 2024 |
| Compuco Ltd | Information & communication | 2006 |
| Computational Mechanics International Limited | Real estate | 1977 |
| Computational Science Limited | Information & communication | 2018 |
| Computer Problems Solved Limited | Information & communication | 2009 |