| Co&Ad Ltd | Professional & scientific | 2014 |
| Co-Work Space Limited | Real estate | 2012 |
| Co-Work Space Two LLP | | 2010 |
| Coach Chris - Peaceful Warrior Ltd | Education | 2024 |
| Coach Hire Directory Ltd | Transport & logistics | 2025 |
| Coach House Ripon Operations Ltd | Administrative & support | 2026 |
| Coach House Ripon Property Limited | Real estate | 2026 |
| COACH2IMPROVE Ltd | Professional & scientific | 2024 |
| Coaching Clever Limited | Professional & scientific | 2017 |
| Coaching Consultancy Limited | Administrative & support | 2003 |
| Coaching East West Limited | Professional & scientific | 2015 |
| Coaching Impact Limited | Other services | 2007 |
| Coastal and City Management Ltd | Professional & scientific | 2018 |
| Cobalt Build Ltd | Transport & logistics | 2020 |
| Cobalt Data Systems Limited | Information & communication | 2006 |
| Coco Nails Spa Ltd | Other services | 2023 |
| Cod&Val Ltd | Construction | 2024 |
| Code Direct Limited | Health & social care | 2014 |
| Code ME Velvet Limited | Information & communication | 2014 |
| Code Ministry Ltd | Information & communication | 2022 |
| Code Simple Limited | Information & communication | 2016 |
| Coded Planet Ltd | Information & communication | 2012 |
| Coderbyte Ltd | Information & communication | 2023 |
| Codevity Limited | Information & communication | 2008 |
| Codicote Indian Spice Ltd | Other services | 2026 |
| Coding and Corrections Ltd | Wholesale & retail | 2024 |
| Cody K9 Ltd | Administrative & support | 2023 |
| COE of Ilford Limited | Wholesale & retail | 1960 |
| Coeurdata Limited | Information & communication | 2009 |
| Coface UK Holdings Limited | Financial services | 1959 |
| Coface UK Services Limited | Financial services | 2000 |
| Coffee Group Limited | Wholesale & retail | 2018 |
| Coffee House 113 Ltd | Hospitality | 2024 |
| Coffee Life Ltd | Real estate | 2022 |
| Coffee With Ella Ltd | Other services | 2023 |
| Coffeewala Ltd | Hospitality | 2020 |
| COGENT1 Ltd | Construction | 2015 |
| Cogitate Data Science Limited | Information & communication | 2019 |
| Cogitate Staffing Limited | Information & communication | 2022 |
| Cogniscience Clinics Ltd | Health & social care | 2025 |
| Coherence Ventures Ltd | Financial services | 2022 |
| Colebrooke (Islington) Flat Company Limited | Real estate | 2001 |
| Coleburt Cars Ltd | Wholesale & retail | 2019 |
| Colecode Ltd | Information & communication | 2015 |
| Colin Gray & Co Limited | Professional & scientific | 2007 |
| Collect Store Analyze Limited | Information & communication | 2014 |
| Collection 1212 Limited | Wholesale & retail | 2003 |
| Collette Consulting Limited | Professional & scientific | 2025 |
| Collheath Computer Services Limited | Information & communication | 2008 |
| Collier & Grant Ltd | Wholesale & retail | 2025 |
| Collins Valley Limited | Real estate | 2024 |
| Colom Ltd | Professional & scientific | 2019 |
| Colorite Limited | Professional & scientific | 2007 |
| Colorite Paint Company Limited | Wholesale & retail | 2000 |
| Colorite Spray Paints Limited | Wholesale & retail | 1994 |
| Colorite.Co.Uk Limited | Professional & scientific | 2000 |
| Colossal Builder Ltd | Construction | 2025 |
| Colour IT Ltd | Construction | 2009 |
| Colpa Precision Engineering Limited | Manufacturing | 1946 |
| Coluco Limited | Hospitality | 2015 |
| Colux Limited | Hospitality | 2001 |
| Colyfield Limited | Professional & scientific | 1997 |
| Comar Constructions Ltd | Construction | 2019 |
| Combat Fitness Ltd | Arts & recreation | 2023 |
| Comfipals Ltd | Wholesale & retail | 2023 |
| Comfort Hotels Limited | Hospitality | 1978 |
| Comi Transport Ltd | Transport & logistics | 2018 |
| Comley Chiropractic Limited | Health & social care | 2006 |
| Commerce Wonderland Ltd | Wholesale & retail | 2024 |
| Commerce World Ltd | Wholesale & retail | 2023 |
| Commercial Alloys Limited | Wholesale & retail | 2007 |
| Commercial and Consulting Services Ltd | Professional & scientific | 2024 |
| Commercial Electrical Systems Ltd | Construction | 2020 |
| Commercial Motors (Watford) Limited | Wholesale & retail | 1966 |
| Common Sense Training Ltd | Administrative & support | 2018 |
| Communal Property Services Limited | Households | 2019 |
| Communal Services Investment Limited | Real estate | 2017 |
| Commune Village Ltd | Wholesale & retail | 2018 |
| Community Connection Projects CIC | Administrative & support | 2014 |
| Community Learning Partnership Limited | Education | 2006 |
| Community Project Consultants Ltd | Professional & scientific | 2020 |
| Community Yoga Project London Limited | Education | 2024 |
| Compact Group Limited | Professional & scientific | 2018 |
| Compact Links Limited | Professional & scientific | 2022 |
| Companion Voices CIC | Education | 2019 |
| Company 6 Ltd | Information & communication | 2012 |
| Company Defence Limited | Professional & scientific | 2019 |
| Compass Culture and Education Ltd. | Education | 2014 |
| Compass Fields (Watford) Management Company Limited | Households | 2018 |
| Compass Vehicle Hire Ltd | Administrative & support | 2026 |
| Compendium Developments Limited | Information & communication | 1998 |
| Complete Animal Care Limited | Professional & scientific | 1996 |
| Complete Detail Limited | Wholesale & retail | 2006 |
| Complete Testing Ltd | Information & communication | 2018 |
| Complete Works & Services Ltd | Construction | 2015 |
| Completely Assured Ltd | Professional & scientific | 2020 |
| Complex Simplicity QA Limited | Information & communication | 2013 |
| Complexjr Ltd | Construction | 2024 |
| Compliance in Action Limited | Professional & scientific | 2014 |
| Compliance Risk and Controls Ltd | Information & communication | 2012 |