| CJ & JG Ltd | Hospitality | 2016 |
| CJ and SON Care Limited | Health & social care | 2024 |
| Cj-Pro Contracting Ltd | Construction | 2013 |
| CJA Estates Ltd | Real estate | 2022 |
| CJG Capital Limited | Professional & scientific | 2025 |
| CJG Ventures Limited | Administrative & support | 2022 |
| CJI Ltd | Real estate | 2019 |
| CK Electrical Solutions Limited | Construction | 2018 |
| CK Traders Ltd | Wholesale & retail | 2020 |
| Ck-Ladim Group Limited | Real estate | 2025 |
| CKK Homes Ltd | Real estate | 2025 |
| CKQ Cleaning Services Ltd | Administrative & support | 2026 |
| Clah Ltd | Hospitality | 2026 |
| Claim Help Limited | Other services | 2009 |
| Clanlead Holdings Limited | Financial services | 2006 |
| Clanlead Limited | Real estate | 1979 |
| CLARA06 Limited | Transport & logistics | 2019 |
| Clarence Properties Luton Ltd | Real estate | 2020 |
| Clarendon Cleaning Ltd | Administrative & support | 2024 |
| Clarendon Court (Luton) Management Limited | Households | 1982 |
| Clarident Ltd | Health & social care | 2023 |
| Claridge & Hall Bros., Limited | Construction | 1938 |
| Clarior Counsel Limited | Professional & scientific | 2024 |
| Claritisolutions Limited | Information & communication | 2012 |
| Clarity Partner Coaching Ltd | Hospitality | 2020 |
| Clashic Jewels Design LLP | | 2022 |
| Class a Cakes Ltd | Manufacturing | 2020 |
| Class a Events Ltd | Hospitality | 2021 |
| Classic Car Solutions Limited | Wholesale & retail | 2017 |
| Classic Executive's Barber Shop Ltd | Other services | 2021 |
| Classics Agenda Limited | Education | 2013 |
| Classy B Ltd | Wholesale & retail | 2024 |
| Claude&Team Ltd | Construction | 2015 |
| Claudio Smart Limited | Wholesale & retail | 2025 |
| Claverley Systems Limited | Information & communication | 2025 |
| Claydon Securities Limited | Real estate | 1956 |
| Clayton Corporate Ltd | Wholesale & retail | 2015 |
| Clayton Cottages Ltd | Real estate | 2023 |
| CLC Couture & Aesthetics Ltd | Manufacturing | 2023 |
| CLD Accident Repairs Ltd | Wholesale & retail | 2019 |
| Clean & Green GMV Ltd | Administrative & support | 2025 |
| Clean Boys Ltd | Administrative & support | 2024 |
| Clean Properties Management Ltd | Construction | 2017 |
| Clean Response Solutions Ltd | Administrative & support | 2015 |
| Clean Slate Construction Services Ltd | Administrative & support | 2024 |
| Clean Warriors Ltd | Administrative & support | 2026 |
| Cleanhut Limited | Administrative & support | 2023 |
| Cleaning an Ltd | Administrative & support | 2025 |
| Cleaning by Cinderella Ltd | Administrative & support | 2020 |
| Cleanr Limited | Wholesale & retail | 2026 |
| Cleanshield Ltd | Administrative & support | 2023 |
| Cleanslatecarrentals Ltd | Administrative & support | 2026 |
| Cleantron Systems Limited | | 1992 |
| Cleanza Ltd | Administrative & support | 2024 |
| Clear Future Properties Ltd | Real estate | 2023 |
| Clear Future Support Ltd | Administrative & support | 2024 |
| Clear Spectrum Ltd | Administrative & support | 2016 |
| Clear View Sound Limited | Information & communication | 2011 |
| Clear Vuln Ltd | Information & communication | 2026 |
| Cleardesk Business Support Ltd | Professional & scientific | 2026 |
| CLEARFLOW247 Ltd | Water & waste | 2025 |
| Clearhead Media Limited | Information & communication | 2008 |
| Clearing Spaces Interiors Ltd | Extraterritorial | 2026 |
| Clearlake Investments Limited | Real estate | 2024 |
| Clearmind Neuro Ltd | Health & social care | 2015 |
| Clearpath Capital Limited | Wholesale & retail | 2025 |
| Clearpoint Consultancy Ltd | Professional & scientific | 2025 |
| Clearsale Properties Ltd | Real estate | 2023 |
| Clearskin Skin Care Limited | Other services | 2021 |
| Clearvale Group Limited | Wholesale & retail | 2026 |
| Clearview Digimart Ltd | Information & communication | 2025 |
| Clearview Estates Limited | Real estate | 2011 |
| Clearvision Photography Limited | Professional & scientific | 2004 |
| Clearway Property Group Limited | Water & waste | 2026 |
| Clee Brothers Ltd | Wholesale & retail | 2011 |
| Clee Brothers Properties Limited | Real estate | 2024 |
| Clee Motor Services Limited | Wholesale & retail | 2026 |
| Clemency Marketing and Communications Ltd | Professional & scientific | 2022 |
| Clemtay and Associate Limited | Health & social care | 2023 |
| Cleo Construction Ltd | Administrative & support | 2024 |
| Cleotrans Limited | Transport & logistics | 2015 |
| Clerqly Ltd | Information & communication | 2025 |
| Cleveland Alan Brown Ltd | Information & communication | 2021 |
| Clever Munchkins Nursery Ltd | Education | 2015 |
| Clever WIN Ltd | Administrative & support | 2024 |
| Cleverdon Enterprises Ltd | Information & communication | 2016 |
| Click & Brit Ltd | Wholesale & retail | 2025 |
| Click 2 Work Limited | Administrative & support | 2025 |
| Click Accountancy Ltd | Professional & scientific | 2022 |
| Click and Go Store Ltd | Wholesale & retail | 2026 |
| Click That Property Ltd | Real estate | 2014 |
| Clickcave Ltd | Wholesale & retail | 2026 |
| Clicknest Traders UK Limited | Wholesale & retail | 2025 |
| CLICKS4US Ltd | Wholesale & retail | 2021 |
| Clicktobuy Limited | Other services | 2020 |
| Cliffords Inn Management Company Limited | Households | 1979 |
| Clifton 1ST Limited | Real estate | 2025 |
| Clifton Foods Ltd | Wholesale & retail | 2022 |
| Clifton Road (Shefford) Ltd | Real estate | 2019 |
| Climate Fuels Ltd | Professional & scientific | 2011 |