| Braiswick (UK) Limited | Professional & scientific | 1987 |
| Braiswick Photographic Company Limited | Professional & scientific | 1965 |
| Brantham Auto Centre Limited | Wholesale & retail | 2010 |
| Brantham Scout and Guide Group Headquarters Development Company Limited | Other services | 2024 |
| Bridgesilver Ltd | Hospitality | 2015 |
| Bright Smiles by LOU Ltd | Health & social care | 2023 |
| Brooks Malting Management Limited | Households | 1998 |
| Brown & Grimsey Property Limited | Real estate | 2014 |
| Brown Waters Picture Films Ltd | Arts & recreation | 2024 |
| Bsah Consultancy Ltd | Professional & scientific | 2015 |
| Bufa Composites UK Ltd. | Wholesale & retail | 1987 |
| Building Blocks Child Care (Dundonald Road) Limited | Education | 2009 |
| Building Blocks Child Care (Fulwell Road) Limited | Education | 2009 |
| Building Blocks Child Care (Kingston Road) Limited | Education | 2009 |
| Building Blocks Child Care Ltd | Education | 2000 |
| Busy Bees Kindergarten CIC | Education | 2009 |
| C & W Fencing Limited | Construction | 1988 |
| C.O. Close Management Company Limited | Households | 1992 |
| C2 Electrical Ltd | Construction | 2025 |
| CAK IT Ltd | Information & communication | 2026 |
| CAK Services Ltd | Real estate | 2025 |
| Cakeversity Ltd | Extraterritorial | 2024 |
| Calectro Engineering Services Limited | Construction | 2012 |
| Cannonbury Electrical Limited | Construction | 2006 |
| Canny Production Limited | Professional & scientific | 2025 |
| Capstan Suffolk LLP | | 2020 |
| Carmel Associates Ltd | Real estate | 2024 |
| Carmichael Aviation Limited | Other services | 2023 |
| Carters Heritage Buses Ltd | Administrative & support | 2012 |
| Castlewood Developments Limited | Construction | 2021 |
| Castor and Partners Limited | Professional & scientific | 2012 |
| Cat UK Vehicle Transportation Limited | Transport & logistics | 1997 |
| CBC Services Ltd | Administrative & support | 2021 |
| Cedar House (Ipswich) Limited | Households | 1981 |
| Central Maltings Management Limited | Households | 1998 |
| CES Social Work Services Limited | Health & social care | 2013 |
| Charlie Oscar Consultancy Ltd | Professional & scientific | 2022 |
| Chemical Dependency LAB Ltd | Wholesale & retail | 2025 |
| China Venture Capital Management Limited | Professional & scientific | 1984 |
| Chris-B Ltd | Hospitality | 2011 |
| Churchmouse Limited | Extraterritorial | 2022 |
| Churchwood Stanley Ltd. | Real estate | 2014 |
| Circuitry PCB Designs Limited | Professional & scientific | 2024 |
| Citex Factors Ltd | Financial services | 2020 |
| Citytrust Accounts Limited | Professional & scientific | 2015 |
| CJA Legal Consultancy Limited | Professional & scientific | 2026 |
| Claret & Brew Ltd | Wholesale & retail | 2024 |
| Claro Tax Solutions Limited | Professional & scientific | 2023 |
| Climate Pro Ltd | Professional & scientific | 2018 |
| Clipit Snipit Ltd | Other services | 2012 |
| CML Translation Ltd | Professional & scientific | 2012 |
| Colchester Denture Studio Limited | Health & social care | 2002 |
| Colchester EV Chargers Ltd | Construction | 2021 |
| Colchester Racing Developments Ltd | Manufacturing | 2013 |
| Coleman Design Ltd | Manufacturing | 2011 |
| Colombian Artisan Coffee Ltd | Wholesale & retail | 2019 |
| Colombian Pure Ltd | Wholesale & retail | 2020 |
| Colourwell Paint Limited | Wholesale & retail | 2023 |
| Comdez Communications Private Limited | Professional & scientific | 2023 |
| Compass Consultancy Ltd | Information & communication | 2007 |
| Complete Drywall and Ceiling Solutions Ltd | Construction | 2025 |
| Complete Planning and Sustainable Development Ltd | Professional & scientific | 2021 |
| Constable Park Ltd | Hospitality | 2018 |
| Consult @ Dragon Ltd | Professional & scientific | 2008 |
| Cora & Cleo Ltd | Manufacturing | 2024 |
| Craig LEE Construction Limited | Construction | 2018 |
| Craigs Clearance Clubs Ltd | Wholesale & retail | 2026 |
| Cranswick Place Management Company Ltd | Real estate | 2020 |
| Creative Juice Collective Limited | Arts & recreation | 2018 |
| Creative Powerhouse East CIC | Education | 2024 |
| Curtis - Allen & Associates Ltd | Health & social care | 2009 |
| Curtis Fire & Safety Limited | Professional & scientific | 2023 |
| CUT 2 Fit Ltd | Manufacturing | 2022 |
| Cyberchief Technologies Ltd | Information & communication | 1997 |
| D P Brooks Limited | Financial services | 2007 |
| D. C. Williamson Limited | Agriculture & fishing | 2000 |
| D. Mcnair Limited | Agriculture & fishing | 1960 |
| Dairy House Farm Limited | Financial services | 2016 |
| Dakas Homes Limited | Wholesale & retail | 2004 |
| Dakko Dakko Ltd. | Information & communication | 2010 |
| Dare to DIP CIC | Other services | 2024 |
| DAT Images Ltd | Construction | 2014 |
| DAT Traffic Safety Ltd | Transport & logistics | 2025 |
| Datum Fabrications Ltd | Manufacturing | 2019 |
| Daves Rails Services Limited | Administrative & support | 2016 |
| David Vaughan Ltd | Financial services | 2018 |
| Davies Global Holdings Ltd | Financial services | 2025 |
| Daynas Hygiene Ltd | Health & social care | 2025 |
| Dcsb Audio Ltd | Information & communication | 2012 |
| Deck Events Limited | Arts & recreation | 2020 |
| Destination Research Limited | Professional & scientific | 2014 |
| DGR Contracts Limited | Construction | 2012 |
| DH Psychology Ltd | Health & social care | 2024 |
| DHG Holiday Lodges Limited | Other services | 2019 |
| Diaxis ENG Ltd | Administrative & support | 2011 |
| Digisense Limited | Information & communication | 1998 |
| Digitaltvinfo.Com Ltd | Information & communication | 2000 |
| DJP (Richmond) Limited | Construction | 2024 |
| Djwinsland Limited | Financial services | 2022 |
| Domicillary Care Services Ltd | Health & social care | 2023 |