| Cherished Moments Cafe CIC | Health & social care | 2025 |
| Cherry Picker Services Ltd | Administrative & support | 2021 |
| Chillesford Lodge Estate Limited | Real estate | 2015 |
| Chilltech Limited | Manufacturing | 2002 |
| Choose Woodbridge C.I.C. | Other services | 2015 |
| Chopen Limited | Real estate | 2024 |
| Chorus Intelligence Limited | Information & communication | 2011 |
| Chris Wormald Associates Limited | Professional & scientific | 2018 |
| Christine Morgan Properties Ltd | Construction | 2019 |
| Christine's Patisserie Ltd | Hospitality | 2015 |
| Christopher Montrose Limited | Wholesale & retail | 2015 |
| Church Hunters Ltd | Arts & recreation | 2024 |
| Cinico Limited | Other services | 2021 |
| Cjis Consultancy Ltd | Professional & scientific | 2025 |
| Clamas Ltd | Hospitality | 2024 |
| Clappits Contractors Limited | Construction | 2012 |
| Clappits Plant Limited | Construction | 2011 |
| Clare Arts and Crafts Limited | Arts & recreation | 2023 |
| Clarity Financial Advisers Limited | Financial services | 2021 |
| Clark & SON (Long Melford) Limited | Manufacturing | 2013 |
| Clark & SON Catering Butchers Limited | Wholesale & retail | 2026 |
| Clark & SON Inns Limited | Hospitality | 2026 |
| Clarke & Simpson Auctions Limited | Real estate | 2013 |
| Classic Football Boots Limited | Wholesale & retail | 2020 |
| Clear Sky Consultancy Limited | Professional & scientific | 2019 |
| Clearwater Capital Investments Limited | Financial services | 2014 |
| Cleatsheet Ltd | Information & communication | 2019 |
| CLM Motors Ltd | Wholesale & retail | 2025 |
| Clonsast Ltd | Real estate | 2024 |
| CM Supply Chain Ltd | Administrative & support | 2024 |
| Cmt.Training Limited | Administrative & support | 2024 |
| Coal Edge Ltd | Other services | 2019 |
| Coast Consulting Limited | Other services | 2009 |
| Coastal Bathrooms & Kitchens Limited | Construction | 2011 |
| Cobra Mist Limited | Information & communication | 2015 |
| Code Therapy Ltd | Information & communication | 2024 |
| Coggeshall Road Therapeutic Provision Limited | Education | 2024 |
| Cohere Arts CIC | Arts & recreation | 2021 |
| Colchester Surgery Centre Limited | Health & social care | 2020 |
| Coldhouse Collective Ltd | Professional & scientific | 2014 |
| Coltec Ltd | Wholesale & retail | 2003 |
| Coltec Racing Engines Limited | Wholesale & retail | 2009 |
| Colyer Holdings Limited | Financial services | 2025 |
| Commercial Finance Brokers UK Limited | Financial services | 2007 |
| Compass Horticulture Ltd | Wholesale & retail | 2017 |
| Compass Rigging Ltd | Manufacturing | 2025 |
| Compz Ltd | Manufacturing | 2025 |
| Comtura Limited | Information & communication | 2021 |
| Concours Classics Limited | Wholesale & retail | 2022 |
| Conduct Cube Limited | Professional & scientific | 2016 |
| Contract PAY Ltd | Administrative & support | 2021 |
| Conway Marsh Garrett Technologies Limited | Manufacturing | 2002 |
| Cookley Ltd | Agriculture & fishing | 2024 |
| COP a Classic Limited | Wholesale & retail | 2021 |
| Copper Kettle Coffee Ltd | Wholesale & retail | 2023 |
| Coreson Engineering Ltd | Professional & scientific | 2023 |
| Corinthian Asset Management Ltd | Real estate | 2015 |
| Cornerstone Residential Limited | Real estate | 2015 |
| Cornicello Vita Ltd | Professional & scientific | 2022 |
| Cornwell Dunnett Limited | Education | 2011 |
| Coterie Developments Limited | Real estate | 2020 |
| Coulter Property Investments Limited | Real estate | 2020 |
| Country Care Anglia Limited | Agriculture & fishing | 1989 |
| COX & COX Property Ltd | Real estate | 2021 |
| COX - Olliff Ltd | Manufacturing | 2008 |
| COX Developments (Ipswich) Limited | Real estate | 1965 |
| CR Wright Consulting Limited | Professional & scientific | 2022 |
| Crafted Carpentry & Construction Ltd | Construction | 2024 |
| Crafted Classics Tuning Ltd | Wholesale & retail | 2017 |
| Craftpatch Ltd | Wholesale & retail | 2014 |
| Craigahulliar Energy Limited | Construction | 2011 |
| Cransford Polythene Limited | Manufacturing | 1987 |
| Crate Limited | Manufacturing | 2022 |
| Creagh Associates Ltd | Professional & scientific | 2015 |
| Creasy Consulting Limited | Financial services | 2012 |
| Create (East of England) Limited Partnership | | 2003 |
| Creative Patient Ltd | Professional & scientific | 2022 |
| Creekhill Wireless Consultancy Limited | Information & communication | 2017 |
| Crescent Stone Ltd | Wholesale & retail | 2022 |
| Crest-Ellington (Management Company) Limited | Real estate | 1999 |
| Cretingham Golf Club Ltd. | Financial services | 1998 |
| Crimson Audio Limited | Information & communication | 2003 |
| Crisp Property Investments Ltd | Real estate | 2020 |
| Croft's Commercial Limited | Professional & scientific | 2020 |
| Croptrade Limited | Professional & scientific | 1987 |
| Crossover Eastern Region Ltd | Construction | 2009 |
| Crown Structures Ltd | Manufacturing | 2024 |
| Cruise Chiropractic Limited | Health & social care | 2015 |
| Cruise Ready Limited | Administrative & support | 2018 |
| Crystal Encounters Ltd | Wholesale & retail | 2015 |
| CS Advanced Hair Limited | Other services | 2023 |
| CSF Group Limited | Administrative & support | 2007 |
| CSF Ventures Limited | Administrative & support | 2018 |
| Cubeultra Limited | Professional & scientific | 1998 |
| Cuil Enterprises Limited | Hospitality | 2010 |
| Cultural Intelligence Limited | Information & communication | 1999 |
| Cummings Building & Renovation Ltd | Construction | 2017 |
| Cupboard Love Home Ltd | Wholesale & retail | 2018 |
| Custom Seating Limited | Manufacturing | 2024 |
| Cutlers Wood Ltd | Agriculture & fishing | 2018 |