| Caley Photography Ltd | Professional & scientific | 2025 |
| Cali Grip Ltd | Construction | 2022 |
| Calibre Car Sales Ltd | Wholesale & retail | 2016 |
| Calibre Homes Limited | Real estate | 1972 |
| Calibre Tooling Limited | Wholesale & retail | 2001 |
| California Close (Highwoods) Management Company Limited | Households | 1985 |
| Call Assist Holdings Limited | Financial services | 2006 |
| Call Assist Limited | Financial services | 1998 |
| Call IT Haulage Ltd | Transport & logistics | 2023 |
| Callidas Consulting Ltd | Administrative & support | 2011 |
| Callie Aiello Limited | Information & communication | 2025 |
| Callisto Aircargo Ltd | Transport & logistics | 2021 |
| Callspeedia Ltd | Wholesale & retail | 2026 |
| Callspill Limited | Extraterritorial | 2001 |
| Calogero Trading Ltd | Wholesale & retail | 2017 |
| Calsim Limited | Administrative & support | 2015 |
| Calum Anderson Consulting Limited | Professional & scientific | 2015 |
| CAM Management Services (Essex) Limited | Professional & scientific | 2016 |
| Camborne Management Company Limited | Households | 2000 |
| Cambridge AI Technologies Ltd | Professional & scientific | 2026 |
| Cambridge Sword Ltd | Arts & recreation | 2016 |
| Camiser Limited | Health & social care | 2014 |
| Cammack Properties Limited | Real estate | 2006 |
| Cammax Precima Limited | Manufacturing | 1988 |
| Campaign to Protect Rural Essex | Other services | 2002 |
| Campbell Court (Colchester) Limited | Real estate | 2011 |
| Campoamor Builders (Ipswich) Limited | Real estate | 2005 |
| Campsite Catering Ltd | Hospitality | 2022 |
| Camputel Limited | Manufacturing | 1999 |
| Camulos Consulting Limited | Professional & scientific | 2024 |
| Camulos Creative Limited | Professional & scientific | 2025 |
| Camulos Kitchens Ltd | Manufacturing | 2024 |
| CAN Partnership Limited | Extraterritorial | 2021 |
| Cana Advisory Limited | Professional & scientific | 2019 |
| Cana Healthcare Ltd. | Health & social care | 2020 |
| Canada Fields Management Co. Limited | Households | 2003 |
| Canal Bidco Limited | Financial services | 2025 |
| Canal Holdco Limited | Financial services | 2025 |
| Canal Midco Limited | Financial services | 2025 |
| Canarinho Ltd | Wholesale & retail | 2016 |
| Canary Europe Services Ltd | Wholesale & retail | 2019 |
| Candfbodyrshoprepair Limited | Wholesale & retail | 2026 |
| Candid Care Services Ltd | Health & social care | 2024 |
| Canfield and SON Facilities Ltd | Construction | 2024 |
| Canine Arthritis Management Ltd | Professional & scientific | 2016 |
| Cann Hall Management Limited | Households | 2011 |
| Cannock Mill Cohousing Colchester Ltd | Real estate | 2009 |
| Cannon Engineering Services Ltd | Professional & scientific | 2024 |
| Cannon Preservation Ltd | Construction | 2015 |
| Cano Bean Magic Repairs Ltd | Other services | 2015 |
| Canon Brickwork Homes Limited | Extraterritorial | 2022 |
| Canon Brickwork Ltd | Construction | 2019 |
| Canon Scaffolding Ltd | Construction | 2023 |
| Canonium Learning Trust | Education | 2013 |
| Cantara Lodge LLP | | 2023 |
| Canton 747 Limited | Hospitality | 2024 |
| Canton Eatery Limited | Hospitality | 2026 |
| Cants of Colchester Limited | Agriculture & fishing | 1924 |
| CAP II Limited | Professional & scientific | 2000 |
| Capable Care Services Ltd | Health & social care | 2023 |
| Capel Plant Holdings Limited | Administrative & support | 1986 |
| Capel Plant Services Limited | Professional & scientific | 1973 |
| Capelspace Limited | Professional & scientific | 1977 |
| Capisphere Limited | Professional & scientific | 2024 |
| Capital Choice Healthcare Limited | Health & social care | 2020 |
| Capital Development Limited | Construction | 1999 |
| Capital Duct Services Ltd | Construction | 2018 |
| Capital Management Nexus Ltd | Transport & logistics | 2025 |
| Capital Markets Intelligence Ltd | Information & communication | 2014 |
| Capital OH Limited | Administrative & support | 2010 |
| Capital Screeding Ltd | Construction | 2022 |
| Capital Square Residents Limited | Households | 1999 |
| Capitald UK Limited | Information & communication | 2019 |
| Capitek Limited | Administrative & support | 2025 |
| Cappa Roofing and Cladding Limited | Construction | 2020 |
| Capps-Coe Building Services Limited | Administrative & support | 2023 |
| Capstone Hill Search Limited | Administrative & support | 2012 |
| Captain Copper Beard Ltd | Manufacturing | 2025 |
| Captain Fantastic East Anglia Ltd | Arts & recreation | 2022 |
| Capture Creative Limited | Information & communication | 2012 |
| Capture Media Agency Ltd | Professional & scientific | 2022 |
| Car and Van Limited | Professional & scientific | 2010 |
| Car Data Labs Ltd | Professional & scientific | 2010 |
| Car Junction Ltd | Wholesale & retail | 2024 |
| Caracal Retail Limited | Wholesale & retail | 2024 |
| Caraconnect Limited | Administrative & support | 2011 |
| Caranx Ignobilis Properties Limited | Real estate | 2024 |
| Caravan Care Services Limited | Wholesale & retail | 2016 |
| Caravan World Limited | Extraterritorial | 2022 |
| Carbo Culture Limited | Professional & scientific | 2021 |
| Carbon NKD Ltd | Extraterritorial | 2020 |
| Carbon Numbers Investments Ltd | Financial services | 2020 |
| Carbon Numbers Limited | Manufacturing | 2012 |
| Carbon Safe Limited | Financial services | 2021 |
| Carcasa Ltd | Wholesale & retail | 2024 |
| Carcelona Yards Limited | Transport & logistics | 2024 |
| Cardea Limited | Real estate | 2026 |
| Cardiff Homecare Services Ltd | Health & social care | 2015 |
| Cardinal House Ltd | Other services | 2021 |
| Cardinal Lofts (Mill) Limited | Construction | 2014 |