| Cognition AM Limited | Administrative & support | 2003 |
| Cognition Finance Consultancy Limited | Professional & scientific | 2020 |
| Coined Limited | Professional & scientific | 2023 |
| Cold Built Ltd | Manufacturing | 2025 |
| Coldsnap Software Limited | Information & communication | 2015 |
| Colin Narbeth & SON Limited | Wholesale & retail | 1975 |
| Colin Smith Ltd | Transport & logistics | 2013 |
| Collaborate Marketing Services Ltd | Professional & scientific | 2004 |
| Collabrix Consultancy Limited | Professional & scientific | 2025 |
| College Yard Management Limited | Households | 1995 |
| Collie Print Limited | Manufacturing | 2009 |
| Collin Works Limited | Information & communication | 2026 |
| Collings Electrical Ltd | Construction | 2014 |
| Collins Coaching and Consultancy Ltd | Education | 2019 |
| Collins Funeral Directors Ltd | Other services | 2022 |
| Colney Butchers Ltd | Wholesale & retail | 2024 |
| Colney Windows & Doors Limited | Other services | 2019 |
| Colorsncurves Ltd | Information & communication | 2014 |
| Colourmein Wellbeing CIC | Education | 2024 |
| Colourmotion Limited | Manufacturing | 2016 |
| Coltech Consulting Limited | Administrative & support | 2019 |
| Colvin Travel Solutions Ltd | Administrative & support | 2022 |
| Comca Technology Limited | Information & communication | 2017 |
| Come Stay Limited | Real estate | 2023 |
| Commercial Industrial Property Solutions Limited | Administrative & support | 2019 |
| Commercial Risk Management Ltd | Administrative & support | 2012 |
| Communication Place Ltd | Professional & scientific | 2017 |
| Communities 1ST Enterprise Ltd | Hospitality | 2026 |
| Community Kitchen Ltd | Hospitality | 2011 |
| Community Systems (North London) Limited | Education | 1993 |
| Compalpha Analytics Ltd | Professional & scientific | 2008 |
| Companion Media Group Ltd | Information & communication | 2022 |
| Compassionate Healthcare & Agency Ltd | Administrative & support | 2024 |
| Compeast Ltd | Information & communication | 2023 |
| Complementary Application Solutions Limited | Information & communication | 1999 |
| Complete Automotive Repair Solutions Limited | Manufacturing | 2025 |
| Complete Communications (Essex) Limited | Wholesale & retail | 1995 |
| Complete Contracts Limited | Construction | 1989 |
| Complete Electrical Compliance Ltd | Construction | 2025 |
| Computer Solutions ALI Ltd | Information & communication | 2017 |
| Comuni AI Ltd | Information & communication | 2025 |
| Concentrify Limited | Information & communication | 2024 |
| Concept Chameleon Limited | Professional & scientific | 2018 |
| Concept Spaces Ltd | Information & communication | 2007 |
| Conceptdash Ltd | Information & communication | 2020 |
| Concrete Track Solutions UK Limited | Construction | 2016 |
| Confetti Magic Limited | Arts & recreation | 2000 |
| Confluence Services Ltd | Information & communication | 2022 |
| Congress VFX Ltd | Information & communication | 2023 |
| Conigi Limited | Information & communication | 2000 |
| Coningsby Court (Freehold) Limited | Households | 2004 |
| Coningsby Court Limited | Households | 1977 |
| Conker Nutmeg Ltd | Wholesale & retail | 2024 |
| Connaught Trading Limited | Construction | 2022 |
| Connected Accounting Limited | Professional & scientific | 2015 |
| Connected Waste Management Ltd | Water & waste | 2024 |
| Connexus Cloud Limited | Information & communication | 2023 |
| Connor Estates (Bros) Ltd | Hospitality | 2023 |
| Conor & Stuart Communications Limited | Information & communication | 2000 |
| Consider Digital Ltd | Professional & scientific | 2020 |
| Consilio Lighting Ltd | Manufacturing | 2019 |
| Consort Digital Finance LLP | | 2018 |
| Consort E3 Limited | Information & communication | 2022 |
| Consorticon Group Ltd | Information & communication | 2020 |
| Consorticon Ltd | Information & communication | 2020 |
| Constructing Better Homes Ltd | Construction | 2021 |
| Construction Cleaning Services Ltd | Construction | 2022 |
| Consult-Wright Ltd | Construction | 2016 |
| Consultify Solutions Limited | Information & communication | 2015 |
| Consumabl Limited | Wholesale & retail | 2019 |
| Contemporary Ventures Ltd | Construction | 2010 |
| Context Systems Ltd | Information & communication | 2025 |
| Continuous Homecare Ltd | Health & social care | 2022 |
| Contrasol Worldwide Projects Ltd | Construction | 2022 |
| Controlo Cargo Services Limited | Transport & logistics | 1977 |
| Conversion Punkt Limited | Professional & scientific | 2024 |
| Cook Services Ltd | Professional & scientific | 2024 |
| Coombe Gardens (Hatfield) Management Company Limited | Households | 2012 |
| Cooper Jeffrey Ltd | Administrative & support | 2003 |
| Cooper Printing Machinery Limited | Manufacturing | 1998 |
| Coopers Gate Management Limited | Households | 2001 |
| COOPERS2 Limited | Professional & scientific | 2011 |
| Copehurst Limited | Real estate | 1982 |
| Copper & Wood Ltd | Wholesale & retail | 2018 |
| Corby Network Services Limited | Information & communication | 2015 |
| Core BID Management Limited | Information & communication | 2010 |
| Core Commercial Solutions Limited | Professional & scientific | 2017 |
| Core Maintain Limited | Construction | 2013 |
| Core Management Limited | Professional & scientific | 1993 |
| Core Self Coaching Limited | Education | 2023 |
| Corehard Limited | Construction | 2000 |
| Corepoint Consultancy Ltd | Other services | 2025 |
| Corflow MCC SPV1 LLP | | 2024 |
| Corker Cars Ltd | Administrative & support | 2017 |
| Corkysis Ltd | Professional & scientific | 2020 |
| Cornered Lifestyle Limited | Arts & recreation | 2026 |
| Cornerstone Eco Tourism Limited | Extraterritorial | 2004 |
| Cornerstone Trading and Consulting Limited | Wholesale & retail | 2024 |
| Cornish Point Wines UK Ltd | Wholesale & retail | 1999 |
| Cosy 4 Walls Ltd | Real estate | 2022 |