| Castle House Management Company (Leighton Buzzard) Limited | Other services | 2001 |
| Castlefield Park (Harlington) Management Company Limited | Households | 2024 |
| Castlegate Chorleywood Management Co Limited | Households | 2014 |
| Catbase Publishing Systems Ltd | Information & communication | 2016 |
| Caterpillar Hill Ltd | Administrative & support | 2021 |
| Catina Court (Stanbridge Road) Management Company Limited | Households | 2008 |
| Catley Technologies Limited | Manufacturing | 2017 |
| Caustics Ltd | Professional & scientific | 2013 |
| Cavendishiq Ltd | Information & communication | 2016 |
| Cawdell Specialist Interiors Ltd | Construction | 2022 |
| Caylin Limited | Financial services | 2022 |
| CB Corp Ltd | Professional & scientific | 2025 |
| CB Electrical & Networking Services Limited | Construction | 2015 |
| Cbddelights Ltd | Wholesale & retail | 2019 |
| Cbict Limited | Education | 2012 |
| CBR Brickwork Limited | Construction | 2016 |
| CBX3 Estate Management Ltd | Real estate | 2005 |
| CCM Consultancy Ltd | Information & communication | 2011 |
| CD Information Services Limited | Administrative & support | 2010 |
| CDC Office Furniture Limited | Wholesale & retail | 2020 |
| CDC Office Services Limited | Wholesale & retail | 2020 |
| Cdvfx Ltd | Construction | 2021 |
| CE Teau UK Limited | Construction | 2014 |
| Cedars (Hazlemere) Management Company Ltd | Households | 2005 |
| Cedarwood Developments Limited | Construction | 2009 |
| Celestial Allstars Ltd | Arts & recreation | 2026 |
| Centrium Commercial Limited | Construction | 2009 |
| Certifex Consulting Ltd | Professional & scientific | 2016 |
| Cewm Ltd | Professional & scientific | 2025 |
| CG Motor Tech Limited | Wholesale & retail | 2018 |
| Cgstransport Ltd | Transport & logistics | 2020 |
| CH Accounting and Consulting Limited | Administrative & support | 2018 |
| CH Metrology Limited | Professional & scientific | 2003 |
| Chaks Private Limited | Construction | 2015 |
| Chalgrave IT Solutions Limited | Information & communication | 2011 |
| Chance 2 Change Community Interest Company | Education | 2019 |
| Chandler's Hair Limited | Other services | 2008 |
| Change and Comms Limited | Professional & scientific | 2025 |
| Chapel Flooring Limited | Wholesale & retail | 2000 |
| Chapman Mediation and Consultancy Limited | Professional & scientific | 2022 |
| Charles Young Group Limited | Administrative & support | 2013 |
| Charles Young Limited | Administrative & support | 2008 |
| Charlewood RTM Co Ltd | Households | 2005 |
| Charlies Body Repairs & Restoration Limited | Wholesale & retail | 2025 |
| Charlotte Harrison Ltd | Professional & scientific | 2025 |
| Charnett Care CIC | Health & social care | 2024 |
| Charnett Company Limited | Professional & scientific | 2019 |
| Chartmoor Estates Limited | Construction | 1978 |
| Chartmoor Holdings Limited | Financial services | 1987 |
| Chasey Consulting Limited | Professional & scientific | 2023 |
| Chat Rubbish Ltd | Water & waste | 2025 |
| Chatell Group Limited | Financial services | 2023 |
| Chatham Capital Partners Ltd | Professional & scientific | 2025 |
| Chayil Communications Ltd | Professional & scientific | 2021 |
| CHD Property Limited | Real estate | 2020 |
| Checkley Homes Limited | Professional & scientific | 1991 |
| Checkley Wood Energy Limited | Energy | 2015 |
| Chedworth Court Limited | Households | 1988 |
| Chelmsford Grass Machinery Limited | Wholesale & retail | 1960 |
| Cherished Skies Ltd | Wholesale & retail | 2024 |
| Chesnut Court (Tring) Freehold Limited | Real estate | 2014 |
| Chestnut (LB) Limited | Construction | 1988 |
| Chestnut Candles Ltd | Manufacturing | 2021 |
| Chestnut Court (Tring) Management Company Limited | Households | 1984 |
| Chestnut Morgan Holdings Ltd | Extraterritorial | 2018 |
| Chestnut-Morgan Ltd | Construction | 2015 |
| Chez a Ltd | Hospitality | 2019 |
| CHF Estates Ltd | Real estate | 2022 |
| CHI Designs Ltd | Information & communication | 2010 |
| Chicken Cyclekit Limited | Wholesale & retail | 1951 |
| Chicken Valley Leighton Ltd | Hospitality | 2026 |
| Child Resource Group Ltd | Health & social care | 2022 |
| Chiltern Audio Limited | Wholesale & retail | 2024 |
| Chiltern Coatings Limited | Construction | 1987 |
| Chiltern Gardens Management Limited | Real estate | 1985 |
| Chiltern Scaffolding Limited | Construction | 2018 |
| Chiltern Telecom Limited | Information & communication | 2003 |
| Chiltern Vale Landrover Club Limited | Other services | 2001 |
| Chimaera Construction Limited | Construction | 2013 |
| Chiron Business Consultancy Ltd | Administrative & support | 2018 |
| Chocolate Box Properties Limited | Real estate | 2022 |
| Chris Boyle Building & Roofing Limited | Construction | 2024 |
| Chris Williams Car Service and Repairs Ltd | Wholesale & retail | 2020 |
| Christchurch House Residents Association (Tring) Limited | Households | 1987 |
| Chubb's Weld & Fabrication Limited | Manufacturing | 2023 |
| Church Green MGT C.I.C. | Households | 2018 |
| Church Road Property (Linslade) Ltd | Extraterritorial | 2023 |
| Church Street Radiology Ltd | Health & social care | 2025 |
| Ciga Limited | Extraterritorial | 2006 |
| CIO in the Boardroom Ltd | Information & communication | 2018 |
| Cirp (U.K.) Limited | Professional & scientific | 1982 |
| City & District Ltd | Real estate | 2021 |
| CJ- Freedomyoga Limited | Education | 2023 |
| CJB Affiliates Ltd | Professional & scientific | 2025 |
| CK Wine Store Limited | Wholesale & retail | 2014 |
| CL Beach Ltd | Professional & scientific | 2023 |
| CL Heating Ltd | Construction | 2020 |
| CL Porter Ltd | Professional & scientific | 2025 |
| Clair Atkinson Consultancy Ltd | Professional & scientific | 2024 |
| Claremont Design Build Ltd | Construction | 2023 |