| Cinch Development Ltd | Education | 2016 |
| Cinelight Ltd | Information & communication | 2024 |
| Cislt Ltd | Health & social care | 2022 |
| Citi Facilities Maintenance Limited | Construction | 2016 |
| Citipaving Company Limited | Mining & quarrying | 2008 |
| CJH Project Services Ltd | Professional & scientific | 2026 |
| CJI Engineering Ltd | Manufacturing | 2021 |
| CKK Electrical Limited | Construction | 2017 |
| Clarendon Home Improvements Ltd | Construction | 2008 |
| Claret Blue Services Limited | Health & social care | 2016 |
| Clarity Hypnosis & Counselling Ltd | Health & social care | 2025 |
| Clark & King Limited | Manufacturing | 1962 |
| Clarks & Sons Ltd | Real estate | 2023 |
| CLB Precast Limited | Construction | 2020 |
| Cleaning Dorset Limited | Administrative & support | 2019 |
| Clear Balance Bookkeeping Limited | Professional & scientific | 2023 |
| Clear Field Sales Ltd | Administrative & support | 2016 |
| Clear Insurance Limited | Financial services | 2011 |
| Clearanceops Ltd | Water & waste | 2020 |
| Clearanswer Call Centres Limited | Administrative & support | 2002 |
| Clearanswer Limited | Other services | 2014 |
| Clearanswer Properties Limited | Real estate | 2010 |
| Clearcut Engraving Limited | Other services | 2015 |
| Clearsprings (Management) Limited | Professional & scientific | 1999 |
| Clearsprings Ready Homes Ltd | Real estate | 2012 |
| Clee Civils & Utilities Ltd | Construction | 2022 |
| Click Business Supplies Ltd | Wholesale & retail | 2021 |
| Clientnet Limited | Information & communication | 2023 |
| Clifftown Consultants Limited | Professional & scientific | 2019 |
| Clinica Fiore Ltd | Health & social care | 2010 |
| Cllandscapes Ltd | Administrative & support | 2025 |
| Cloud 9 Creative Production Ltd. | Arts & recreation | 2013 |
| Cloud Based Utilities LLP | | 2025 |
| Clouds Financial Services Limited | Real estate | 2006 |
| Cloverleaf Construction Services Limited | Construction | 2007 |
| CLR HR Consultancy Ltd | Administrative & support | 2025 |
| CLS Money Limited | Financial services | 2011 |
| CMB Property Limited | Real estate | 2021 |
| Coastline Construction (Essex) Ltd | Construction | 2016 |
| Coastline Developments Essex Limited | Construction | 2014 |
| Coco Nails Bar Limited | Other services | 2019 |
| Coco Wedding Collective Limited | Information & communication | 2017 |
| Coffee Allday Ltd | Information & communication | 2014 |
| Cojahm Limited | Real estate | 2018 |
| Coleman Transport Ltd | Transport & logistics | 2016 |
| Collaboration Ltd | Professional & scientific | 2025 |
| Collins Way Ltd | Administrative & support | 2016 |
| Colosseo Hove Restaurant Limited | Hospitality | 2021 |
| Colourcraft Autos Ltd | Wholesale & retail | 2010 |
| Colourfast Financial Ltd | Manufacturing | 2008 |
| Commandline Consulting Ltd | Information & communication | 2025 |
| Commercial Kitchen Management Ltd | Professional & scientific | 2009 |
| Commercial Mortgage Concierge Ltd | Financial services | 2016 |
| Compare Online Ltd | Administrative & support | 2015 |
| Compass Property Finance Limited | Financial services | 2025 |
| Complete Transmissions Ltd | Wholesale & retail | 2015 |
| Complete Waste Services Limited | Arts & recreation | 1996 |
| Compliant Fire Doors (Essex) Ltd | Construction | 2023 |
| Conerstone Properties Limited | Real estate | 2021 |
| Conquest Creative Spaces Limited | Administrative & support | 2015 |
| Construction Sport Contracts Ltd | Construction | 2023 |
| Constructive Solutions (London) Ltd | Professional & scientific | 2021 |
| Consult LD Ltd | Health & social care | 2016 |
| Consult to Comply Ltd | Construction | 2024 |
| Consumer Magazine Ltd | Information & communication | 2023 |
| Content IT Solutions Limited | Information & communication | 2010 |
| Contented People Limited | Health & social care | 2018 |
| Conway Court (Southend on Sea) Management Company Limited | Households | 2009 |
| Cool Air Conditioning Ltd | Construction | 2016 |
| Cooling Point Services Limited | Administrative & support | 2022 |
| Copestick Consultancies Ltd | Professional & scientific | 2012 |
| Coping Superstore Ltd | Wholesale & retail | 2019 |
| Copper Street Brewery Ltd | Manufacturing | 2022 |
| Copyjim Ltd | Professional & scientific | 2010 |
| Coralie 123 Limited | Other services | 2020 |
| Core 4 Solutions Ltd | Construction | 2018 |
| Core Power Systems Limited | Manufacturing | 2014 |
| Corpex Building Solutions Ltd | Construction | 2026 |
| Corrilan IT Consultancy Ltd | Information & communication | 2005 |
| Cosmic Tour Limited | Administrative & support | 2025 |
| COST2BUILD Consultancy T/A C2B Ltd | Professional & scientific | 2019 |
| Costume 2000 Limited | Arts & recreation | 1999 |
| Country Paws Club Ltd | Other services | 2026 |
| Countryside Escapes Ltd | Real estate | 2024 |
| Courite Investments Limited | Real estate | 1963 |
| Courts of Rayleigh Florist Ltd | Wholesale & retail | 2022 |
| Cowfish Ltd | Information & communication | 2016 |
| CP24 Limited | Administrative & support | 2013 |
| CPC Europe Limited | Arts & recreation | 1991 |
| CPF Roofing & Guttering UK Ltd | Construction | 2025 |
| Crab Shed Studio Limited | Professional & scientific | 2019 |
| Craig Hancock Services Limited | Construction | 2024 |
| Creating Sector Leaders Limited | Extraterritorial | 2022 |
| Creekview Electronics Ltd | Manufacturing | 2011 |
| Cresco Wood Works Limited | Manufacturing | 2015 |
| Croft Futures Limited | Financial services | 2006 |
| Cropaid International Limited | Administrative & support | 2005 |
| Crossways Consultancy (South East) Limited | Professional & scientific | 2016 |
| Crown Finance Limited | Financial services | 2000 |
| Crown Holding Properties Ltd | Real estate | 2021 |