| Coffee Tree Bucks Limited | Hospitality | 2023 |
| Cojinvest Limited | Construction | 2019 |
| Cold Cure Windows Limited | Manufacturing | 1998 |
| Coldene Castors Limited | Manufacturing | 2005 |
| Coldham Consultancy Ltd | Professional & scientific | 2011 |
| Coldham Properties Limited | Real estate | 2013 |
| Cole & Sons Ltd | Construction | 2022 |
| Coley Draughting Services Ltd | Other services | 2013 |
| Colfor Ltd | Real estate | 2025 |
| COLINJACKPMCONSULTANCY1877 Ltd | Information & communication | 2025 |
| Collaborative Conferences Ltd | Administrative & support | 2014 |
| College Lane Solar Farm Limited | Construction | 2025 |
| Collett Farm Limited | Agriculture & fishing | 1943 |
| Collison Tree Care Ltd | Agriculture & fishing | 2017 |
| Collyer Motor Sport Limited | Extraterritorial | 2024 |
| Colosseo Property Investment Limited | Construction | 1964 |
| Colour Palette Interior Design Ltd | Administrative & support | 2019 |
| Colour Palette Interiors Ltd | Administrative & support | 2024 |
| Colour Passion 18 Ltd | Other services | 2026 |
| Colt Staplers Limited | Extraterritorial | 1988 |
| Colton Ashburn Limited | Construction | 2018 |
| Combined Integrated Systems Limited | Administrative & support | 2004 |
| Combo Restaurant Limited | Hospitality | 2025 |
| Comfort Airport Transfer Ltd | Transport & logistics | 2023 |
| Commercial Advice Services Limited | Professional & scientific | 2007 |
| Commercial Vehicle Lubricant Solutions Limited | Professional & scientific | 2020 |
| Commercials Direct Limited | Wholesale & retail | 2014 |
| Commissioning (Water Treatment) Technical Services Ltd | Construction | 2015 |
| Commissioning Management Services Ltd | Construction | 2018 |
| Committed Care Housing CIC | Health & social care | 2019 |
| Common Solutions Ltd | Administrative & support | 2025 |
| Common Table PVT Ltd | Hospitality | 2026 |
| Community Canteen Ltd | Hospitality | 2026 |
| Community Fightback CIC | Administrative & support | 2026 |
| Community Impact Bucks | Health & social care | 1998 |
| Community Impact Bucks (Trading) Ltd | Professional & scientific | 2011 |
| Community Unity Projects | Health & social care | 2012 |
| Comp Room Media Ltd | Manufacturing | 2002 |
| Compactlaw Limited | Information & communication | 1996 |
| Companion Accountancy and Business Services Limited | Professional & scientific | 2006 |
| Company Casa Ltd | Real estate | 2025 |
| Comparison Creator Limited | Administrative & support | 2010 |
| Compclassic Limited | Professional & scientific | 2013 |
| Competition Engines Limited | | 1992 |
| Compiongws Ltd | Information & communication | 2026 |
| Complete Care Always Ltd | Health & social care | 2025 |
| Complete Ceiling & Partitioning Systems Limited | Construction | 1999 |
| Complete Design Solutions Limited | Wholesale & retail | 1994 |
| Complete ID Limited | Information & communication | 2012 |
| Complete Online Backups Ltd | Information & communication | 2011 |
| Complete Packaging Limited | Manufacturing | 1998 |
| Complete Stone Limited | Manufacturing | 2019 |
| Compliant Medical Solutions Ltd | Professional & scientific | 2013 |
| Compressors & Pneumatic Systems Limited | Manufacturing | 2007 |
| Computing 4 U Limited | Information & communication | 2003 |
| Concrete Jungle Fashion Limited | Wholesale & retail | 2015 |
| Condor Lending Ltd | Administrative & support | 2023 |
| Condotta Limited | Information & communication | 2021 |
| Conifer Flats Management (Aylesbury) Limited | Households | 1982 |
| Connect 2 Flexicare Limited | Administrative & support | 2016 |
| Connect Appsforall Limited | Information & communication | 2019 |
| CONNECT2PA'S Limited | Administrative & support | 2014 |
| Connected Cleaning Services Ltd | Administrative & support | 2023 |
| Connected Software Solutions Ltd | Information & communication | 2010 |
| Conneely Corporation Ltd | Administrative & support | 2010 |
| Conner Solutions Ltd | Information & communication | 2009 |
| Connexaire Ltd | Professional & scientific | 2023 |
| Connolly Plumbing & Heating Ltd | Construction | 2023 |
| Connor Mechanical Services Limited | Transport & logistics | 1973 |
| Conosur Experiences Ltd | Administrative & support | 2022 |
| Conrad Court RTM Company Ltd | Households | 2025 |
| Consegno Ltd | Professional & scientific | 2016 |
| Conserve & Restore Limited | Construction | 2020 |
| Consilia Consultants Ltd | Education | 2016 |
| Consoul Ltd | Administrative & support | 2022 |
| Conspec Contracts Limited | Construction | 1990 |
| Consto Global Ltd | Wholesale & retail | 2018 |
| Construct Elevation Ltd | Real estate | 2025 |
| Construction Specialties (U.K.) Limited | Manufacturing | 1975 |
| Constructive Building Services Ltd | Construction | 2024 |
| Constructive Design Ltd | Construction | 2002 |
| Consultant Doctors Limited | Professional & scientific | 2003 |
| Consumer Chemistry Limited | Professional & scientific | 2012 |
| Content Clever Limited | Professional & scientific | 2023 |
| Conversation LAB Ltd | Professional & scientific | 2014 |
| Convocation Limited | Professional & scientific | 2025 |
| Cooci Associates LLP | | 2009 |
| Cooci Rehabilitation Services Limited | Health & social care | 2009 |
| Cook Family Ltd | Information & communication | 2017 |
| Cooke-Fraser Consultancy Ltd | Professional & scientific | 2012 |
| Coopers Car Transport Ltd | Wholesale & retail | 2023 |
| Coopers Recovery Ltd | Wholesale & retail | 2016 |
| Copac & Co Limited | Financial services | 2015 |
| Copac (Aylesbury) Limited | Extraterritorial | 2008 |
| Copac Limited | Extraterritorial | 2015 |
| Copernicus Lyceum Ltd | Professional & scientific | 2026 |
| Copper Mill Down Limited | Real estate | 1990 |
| Copper Penny Box Limited | Hospitality | 2023 |
| Copperway Ltd | Construction | 2021 |
| Copse & Woodland Management Limited | Agriculture & fishing | 2010 |