| Croftmore Consultancy Limited | Health & social care | 2011 |
| Croissant Ltd | Real estate | 2015 |
| Crosby Agri Limited | Agriculture & fishing | 2010 |
| Crosby Fields HR Limited | Administrative & support | 2016 |
| Crosley & SON Limited | Extraterritorial | 2000 |
| Cross Border Partners Limited | Professional & scientific | 2023 |
| Cross ITM Limited | Information & communication | 2025 |
| Crossfit Battlebox Limited | Other services | 2013 |
| Crossways Manor Road Ltd | Households | 2015 |
| Crouch Renovations Limited | Real estate | 2019 |
| Crouch Ridge Estate Ltd | Wholesale & retail | 2020 |
| Crouch Ridge Ltd | Hospitality | 2024 |
| Crouch Vale Brewery Limited | Manufacturing | 1980 |
| Crouch Valley Audio Visual Ltd | Other services | 2018 |
| Crovia Ltd | Information & communication | 2026 |
| Crowd Scout International Ltd | Information & communication | 2025 |
| Crown Concierge Ltd | Administrative & support | 2018 |
| Crown Consumer Limited | Hospitality | 1996 |
| Crown Event Catering & Hire Ltd | Hospitality | 2011 |
| Crown House Homes (Colchester) Ltd | Real estate | 2015 |
| Crown Ingatestone Limited | Construction | 2014 |
| Crown Leather Co. Ltd | Wholesale & retail | 2026 |
| Crowned Beauty CB Limited | Other services | 2023 |
| Crownoak Business Ltd. | Transport & logistics | 2013 |
| Crows Lane Estate Limited | Agriculture & fishing | 2019 |
| Croydon Golf Limited | Arts & recreation | 1996 |
| CRS Auto Fabrication Limited | Wholesale & retail | 2023 |
| Crub Limited | Construction | 2025 |
| Crumstor Limited | Professional & scientific | 2015 |
| Cryptonative Systems Limited | Information & communication | 2023 |
| Crystal 29 Healthcare Ltd | Health & social care | 2024 |
| Crystal Cleaning Services Limited | Professional & scientific | 2002 |
| Crystal Coven Ltd | Wholesale & retail | 2023 |
| Crystal Nails NO1 Ltd | Education | 2014 |
| Crystal Properties (Essex) Ltd | Construction | 2023 |
| Crystallised HR Ltd | Administrative & support | 2020 |
| CS 77 Consulting Ltd | Professional & scientific | 2024 |
| CSC Wealth Planning Limited | Professional & scientific | 2012 |
| CSI Electronic Manufacturing Services Limited | Manufacturing | 2024 |
| CSJ Talent Solutions Ltd | Administrative & support | 2026 |
| CSL Building Solutions Ltd | Construction | 2024 |
| CSM Accountancy Ltd | Professional & scientific | 2022 |
| CSO Engineering Limited | Administrative & support | 2023 |
| CSO Marine Group Limited | Financial services | 2018 |
| CSO Shipbrokers Ltd | Administrative & support | 2016 |
| CSP Temple Ltd | Real estate | 2024 |
| CSR Health Limited | Health & social care | 2025 |
| CT Cable Jointing Limited | Construction | 2021 |
| CT Housing Ltd | Real estate | 2025 |
| CT Solar Ltd | Construction | 2025 |
| Ct&R Technical Services Limited | Administrative & support | 2021 |
| CTD Education Limited | Education | 2026 |
| Ctfg Kirkwood Limited | Construction | 2025 |
| CTH Mechanical Services Ltd | Construction | 2011 |
| CTM Supplies Ltd | Administrative & support | 2016 |
| Ctprops Limited | Real estate | 2025 |
| Cube Intelligence Analytics Ltd | Information & communication | 2024 |
| Cube Property Developers Ltd | Construction | 2021 |
| Cube Surveying Ltd | Real estate | 2011 |
| CUE AI Limited | Information & communication | 2025 |
| Cullings Construction Ltd | Construction | 2011 |
| Cullum Limited | Financial services | 1984 |
| Culmination 2 Limited | Professional & scientific | 2026 |
| Culmination Limited | Professional & scientific | 2022 |
| Cultmag Ltd | Arts & recreation | 2024 |
| Cunningham Lasmanis Limited | Wholesale & retail | 2024 |
| Curds Farm Estate Management Limited | Real estate | 2023 |
| Cure & Secure Limited | Real estate | 2021 |
| Curechem Ltd | Wholesale & retail | 2008 |
| Curiosities From the Fifth Corner Ltd | Wholesale & retail | 2021 |
| Curiouser and Curiouser Pictures Ltd | Information & communication | 2018 |
| Curley Brackets Engineering Limited | Information & communication | 2018 |
| Curlio Limited | Information & communication | 2009 |
| Curnott Management Services Limited | Administrative & support | 2006 |
| Curo Underwriting Services Ltd | Financial services | 2015 |
| Currock Engineering Company Limited | Manufacturing | 1964 |
| Curry & Go Ltd | Hospitality | 2025 |
| Curry Classes Limited | Extraterritorial | 2009 |
| Curry's Distribution Co. Limited | Wholesale & retail | 1999 |
| Curtain Works Ltd | Professional & scientific | 2012 |
| Customised Landscapes and Interiors Ltd | Administrative & support | 2025 |
| Customswrap Limited | Construction | 2015 |
| CUT Line Risk Management Limited | Professional & scientific | 2017 |
| CUT, Slice & Skim Limited | Extraterritorial | 2021 |
| Cutpoint Carpentry Ltd | Construction | 2025 |
| Cutter Store Ltd | Wholesale & retail | 2024 |
| Cutting Edges Limited | Other services | 1994 |
| Cutting Properties Ltd | Real estate | 2023 |
| Cuturi Gallery UK Limited | Wholesale & retail | 2022 |
| CVA Education Consultancy Ltd | Education | 2018 |
| CVC Chelmer Valve Company Limited | Wholesale & retail | 2019 |
| CVC Components Ltd | Manufacturing | 2002 |
| CVJ Group Limited | Information & communication | 2023 |
| CVK Buildtech Limited | Construction | 2025 |
| CWA Technology Ltd | Information & communication | 2024 |
| CWC Solutions Ltd | Health & social care | 2018 |
| CWM Electrical Ltd | Construction | 2016 |
| CWR Solutions Limited | Professional & scientific | 2011 |
| CYB3RINTELLIGENCE Ltd | Information & communication | 2019 |
| Cycle Sanctuary Ltd | Manufacturing | 2019 |