| BY Roqa Ltd | Other services | 2024 |
| Byme Productions Ltd | Information & communication | 2026 |
| BZR Property Limited | Real estate | 2024 |
| C & C Developments Fleetwood Ltd | Professional & scientific | 2006 |
| C J Mendes Limited | Professional & scientific | 2023 |
| C Tribe Consulting Services Limited | Professional & scientific | 2026 |
| C Tribe Housing Limited | Real estate | 2025 |
| C Tribe Property Limited | Real estate | 2020 |
| C&G Engineering Ltd | Manufacturing | 2020 |
| C-Suite Consulting.Com Limited | Professional & scientific | 2017 |
| C.A.S. Limited | Professional & scientific | 1998 |
| C.J. O'Shaughnessy (Brickwork) Limited | Construction | 2001 |
| C.S. Building & Design Limited | Construction | 1997 |
| C.T.S. Studio Limited | Professional & scientific | 2024 |
| C.W. JOE Limited | Extraterritorial | 2023 |
| Cabrillo Limited | Professional & scientific | 2019 |
| Cactus Accounting Ltd | Professional & scientific | 2023 |
| Caer Urfa Limited | Professional & scientific | 2003 |
| Cairngorm LDA Limited | Financial services | 2025 |
| Cairngorm Vitality Limited | Wholesale & retail | 2024 |
| Calalogic Limited | Wholesale & retail | 2025 |
| Calceum Limited | Information & communication | 2026 |
| Calliope Communications Ltd | Professional & scientific | 2023 |
| Calloway Group Limited | Professional & scientific | 2010 |
| Calver and Wolf Limited | Wholesale & retail | 2017 |
| CAM Square (Hitchin) Management Company Ltd | Administrative & support | 1987 |
| CAN. Will. DID. Limited | Professional & scientific | 2025 |
| Caonefour Limited | Arts & recreation | 2015 |
| Cape Burford Construction Services Ltd | Construction | 2025 |
| Cape Clear Solutions Limited | Professional & scientific | 2015 |
| Capron Road Management Company Limited | Households | 2006 |
| Capsule Brands Ltd | Wholesale & retail | 2025 |
| Car Saints Ltd | Wholesale & retail | 2025 |
| Care IMA International Limited | Administrative & support | 1989 |
| Careers in Sport Ltd | Professional & scientific | 2024 |
| Caremore Homes Limited | Construction | 2015 |
| Carlow Court Freehold Limited | Real estate | 2017 |
| Carlton Road Developments (Harpenden) Limited | Construction | 1966 |
| Carne Erris Construction Ltd | Construction | 2017 |
| CAS Financial Planning Ltd | Financial services | 2021 |
| Casa Mentmore Ltd | Real estate | 2020 |
| Cassiano Holdings Limited | Real estate | 2025 |
| Castle Mill Apartments Limited | Households | 2005 |
| Castle Point Consulting Ltd | Information & communication | 2025 |
| Catherine Potter Physiotherapy Limited | Health & social care | 2009 |
| Catherine Redmond Consulting Limited | Professional & scientific | 2017 |
| Cavant Limited | Professional & scientific | 2016 |
| Cavendish Arms Management Company Ltd | Real estate | 2024 |
| Cayenne Associates Limited | Professional & scientific | 2013 |
| CBG Developments Limited | Real estate | 2024 |
| CC Hair Ltd | Other services | 2024 |
| CD Drywall Ltd | Construction | 2022 |
| Cedar Spaces Ltd | Construction | 2019 |
| Cedars (Maintenance) 2015 Limited | Households | 2015 |
| Cedars (Maintenance) Limited | Households | 1966 |
| Celsation International Limited | Information & communication | 2020 |
| Cenos Blockchain Limited | Information & communication | 2023 |
| Ceres Accountants Ltd | Professional & scientific | 2019 |
| Cervus Limited | Professional & scientific | 2016 |
| CES Electrical Ltd | Construction | 2008 |
| CFA Management Company Ltd | Administrative & support | 2020 |
| CFG Consulting Limited | Administrative & support | 2021 |
| CGP Properties Ltd | Real estate | 2016 |
| CHA CHA CHA Restaurants Ltd | Hospitality | 2021 |
| Chain Brain Ltd | Information & communication | 2017 |
| Change Outcomes Limited | Professional & scientific | 2014 |
| Chapter International Ltd | Administrative & support | 2019 |
| Charlie Cullen Creative Limited | Other services | 2025 |
| Charlotte James Property Limited | Real estate | 2022 |
| Charlston Goch Associates Limited | Professional & scientific | 2023 |
| Chase Independence Ltd | Health & social care | 2018 |
| Chastons Limited | Construction | 1992 |
| Chateau Heart Limited | Real estate | 2010 |
| Chatsworth Ventures Limited | Real estate | 2022 |
| Chaucer Close (Harpenden) Limited | Real estate | 2010 |
| Chavanette Investments | Financial services | 2015 |
| Chenies Court Associates Limited | Households | 1995 |
| Chepstow Flats Residents Association Limited(The) | Administrative & support | 1978 |
| Cherrytree Livery Yard Limited | Arts & recreation | 2017 |
| Chetna Patel Consulting Ltd | Professional & scientific | 2023 |
| Chez Brooks Consulting Limited | Information & communication | 1998 |
| Childs Hill Developments Limited | Construction | 2015 |
| Chilli JAM Limited | Arts & recreation | 2023 |
| Chillnana Limited | Hospitality | 2025 |
| Chiltern Court (Harpenden) Management Co Limited | Real estate | 1992 |
| Chloe Blanc Ltd | Professional & scientific | 2021 |
| Choice Financial Services (ST Albans) Ltd | Administrative & support | 2003 |
| Christina Consulting Limited | Administrative & support | 2024 |
| Christopher Harwood Limited | Professional & scientific | 2021 |
| Citix Technologies Limited | Information & communication | 2023 |
| City Advertising Limited | Professional & scientific | 2004 |
| City Law Recruitment Limited | Administrative & support | 2012 |
| City Surveying Services Limited | Construction | 2025 |
| CJ Property Management & Development Ltd | Households | 2019 |
| CJB Legal Services Limited | Professional & scientific | 2019 |
| CJS Consultancy Limited | Administrative & support | 2002 |
| CJS IP Limited | Information & communication | 2011 |
| CJS Landscape & Design Limited | Administrative & support | 2022 |
| CK Advisory Limited | Real estate | 2020 |
| CK Capital Group Ltd | Information & communication | 2024 |