| Colchester Ventures Ltd | Wholesale & retail | 2020 |
| Colchester Waste Collection Limited | Water & waste | 2021 |
| Colchester Weightlifting Ltd | Arts & recreation | 2020 |
| Colchester Windows & Plastic Suppliers Limited | Manufacturing | 2013 |
| Colchester Windows Ltd | Extraterritorial | 2024 |
| Colchester Youth Arts Partnership | Education | 1999 |
| Colchester Zoological Society | Administrative & support | 2004 |
| Cold Salad and Ice Cream Ltd | Hospitality | 2026 |
| Coldhand Bristol Ltd | Wholesale & retail | 2025 |
| Coldron Construction Consultants Limited | Professional & scientific | 2026 |
| Colehouse Ltd | Professional & scientific | 2005 |
| Coles Design & Services Limited | Professional & scientific | 2021 |
| Coles Management Ltd. | Administrative & support | 2008 |
| Colewells Property Ltd | Real estate | 2024 |
| Colin Greer Logistic Support Services Limited | Transport & logistics | 2023 |
| Colin Hull Financial Services Ltd | Financial services | 2009 |
| Coll Computing Limited | Information & communication | 2005 |
| Collier & Glynne Limited | Financial services | 2012 |
| Collier Group (Essex) Limited | Wholesale & retail | 2019 |
| Collier Hire Limited | Administrative & support | 2026 |
| Collier Root Holdings Ltd | Financial services | 2025 |
| Collingbourne 270 Limited | Professional & scientific | 2024 |
| Collins Cleaning Services Limited | Administrative & support | 2003 |
| Collins Marine Ltd | Manufacturing | 2021 |
| Collins Pubs Co Ltd | Hospitality | 2024 |
| Collison and Sons Ltd | Construction | 2015 |
| Collison Brickwork Ltd | Construction | 2014 |
| Colne Aviation Ltd | Manufacturing | 2023 |
| Colne Brickwork Ltd | Construction | 2025 |
| Colne Brothers Films Ltd | Arts & recreation | 2017 |
| Colne Carpentry & Joinery Limited | Administrative & support | 2010 |
| Colne Commercials Ltd | Wholesale & retail | 2013 |
| Colne Consulting Ltd | Professional & scientific | 2021 |
| Colne Data & AI Limited | Information & communication | 2024 |
| Colne Developments Limited | Arts & recreation | 1998 |
| Colne Engaine Construct Ltd | Construction | 2023 |
| Colne Forklifts Limited | Other services | 2017 |
| Colne Limited | Administrative & support | 2011 |
| Colne Maintenance Dredging Limited | Transport & logistics | 2019 |
| Colne Mechanical Services Limited | Energy | 2003 |
| Colne Mini Skips | | 1988 |
| Colne Place Gardens Management Company Limited | Households | 2025 |
| Colne Radio Community Interest Company | Information & communication | 2011 |
| Colne Roofing and Cladding Ltd | Construction | 2012 |
| Colne Smart Repairs Ltd | Wholesale & retail | 2015 |
| Colne Stoves & Fireplaces Ltd. | Other services | 1994 |
| Colne Valley Aesthetics Ltd | Other services | 2024 |
| Colne Valley Building Services Limited | Construction | 2005 |
| Colne Valley Design & Consultancy Limited | Professional & scientific | 2022 |
| Colne Valley Electrical (North) Ltd | Construction | 2008 |
| Colne Valley Electrical (South) Limited | Construction | 2007 |
| Colne Valley Electrical Limited | Construction | 1991 |
| Colne Valley Fencing Limited | Construction | 2019 |
| Colne Valley Group Holdings Ltd | Financial services | 2025 |
| Colne Valley Holdings Ltd | Financial services | 2019 |
| Colne Valley Luxury Toilets Ltd | Administrative & support | 2012 |
| Colne Valley Mechanical (North) Limited | Construction | 2025 |
| Colne Valley Mechanical Limited | Construction | 2017 |
| Colne Valley Restorations Ltd | Construction | 2018 |
| Colne Valley Site Services Ltd | Construction | 2017 |
| Colne Valley Tree Services Limited | Administrative & support | 2013 |
| Colneview (Management) Limited | Households | 2007 |
| Colnewell Limited | Professional & scientific | 1978 |
| Colombo Ltd | Health & social care | 2020 |
| Colonia Park (Colchester) Management Company Limited | Households | 1989 |
| Colonial Park Management Company Limited | Households | 2007 |
| Colorvision Ltd | Information & communication | 2022 |
| Colourfast World Holdings Ltd | Financial services | 2020 |
| Colourfast World Limited | Administrative & support | 2003 |
| Coltrax Services Limited | Wholesale & retail | 2026 |
| Colvettia Ltd | Households | 2025 |
| Colyer Transport Limited | Transport & logistics | 2011 |
| Combat Fire Solutions Ltd | Public administration | 2024 |
| Combined Network Solutions Limited | Information & communication | 2019 |
| Comfort Apartments Limited | Real estate | 2023 |
| Comfort Care Services (Colchester) Limited | Health & social care | 1997 |
| Comfort Circle Care Recruitment Ltd | Administrative & support | 2025 |
| Comfort Services Group Limited | Construction | 2006 |
| Comicsure Limited | Financial services | 2024 |
| Command Resilience UK Ltd | Education | 2022 |
| Commercial & Legal Services (UK) Limited | Information & communication | 1988 |
| Commercial and Legal Services Limited | Extraterritorial | 1999 |
| Commercial Insurance Consultants Ltd | Other services | 2019 |
| Commercial Law Consultants Ltd | Administrative & support | 2017 |
| Commissioning Management Limited | Construction | 1983 |
| Commodity Consulting Ltd | Other services | 2026 |
| Commodity Movers Ltd | Wholesale & retail | 2025 |
| Community Media Sports CIC | Other services | 2023 |
| COMMUNITY360 | Other services | 2002 |
| Compact Storage Limited | Manufacturing | 1995 |
| Compact Storage Products Limited | Manufacturing | 1996 |
| Compact Storage Systems Limited | Manufacturing | 1996 |
| Company Name Here Ltd | Information & communication | 2022 |
| Company of Veteran Motorists Limited(The) | Other services | 1935 |
| Compare Trade Finance.Com Ltd | Professional & scientific | 2016 |
| Compass: Consultants, Training & Simulation Limited | Administrative & support | 2016 |
| Compassionate Communication Limited | Health & social care | 2024 |
| Compassiontc Limited | Public administration | 2020 |
| Complete Community Support (East) Limited | Health & social care | 2009 |
| Complete Flooring of Colchester Ltd | Wholesale & retail | 2005 |