| Csorc Ltd | Arts & recreation | 2025 |
| CSS Marketing Ltd | Education | 2014 |
| CSV Technologies Ltd | Information & communication | 2019 |
| Csyde Consulting Ltd | Information & communication | 2026 |
| Csync Ltd | Information & communication | 2026 |
| CT Centre MK Ltd | Health & social care | 2021 |
| CT Consult Properties Ltd | Real estate | 2013 |
| CT Enterprise Holdings Limited | Financial services | 2021 |
| CT Marketing Results Ltd | Professional & scientific | 2025 |
| CT Sparks Ltd | Construction | 2016 |
| CT500 Ltd | Wholesale & retail | 2007 |
| CTC Aviation Limited | Other services | 2020 |
| Ctdi Glenrothes Limited | Manufacturing | 1977 |
| Ctdi Huntingdon Ltd | Information & communication | 1997 |
| Ctdi Milton Keynes Ltd | Information & communication | 2000 |
| Ctdi Repair Services Limited | Manufacturing | 2016 |
| CTE365 Limited | Information & communication | 2021 |
| CTL Plumbing Limited | Construction | 2015 |
| CTL Property Holdings Ltd | Real estate | 2026 |
| CTM Pest Control Limited | Administrative & support | 2012 |
| Ctmk Trading Limited | Wholesale & retail | 2025 |
| Ctrl ALT Decor Ltd | Wholesale & retail | 2025 |
| Ctrl+Impact Ltd | Professional & scientific | 2025 |
| CTS Energy MK Ltd | Other services | 2013 |
| CTS Transport Group Ltd | Transport & logistics | 2004 |
| Ctsventures Ltd | Manufacturing | 2012 |
| Cttk Limited | Real estate | 2024 |
| CTZ Logistics Limited | Transport & logistics | 2024 |
| Cube Estate Developments Ltd | Construction | 2019 |
| Cube Property Solutions Limited | Households | 2017 |
| Cubian Ltd | Hospitality | 2017 |
| Cubic Design and Engineering Ltd | Construction | 2011 |
| Cubic Services Limited | Transport & logistics | 2015 |
| Cucu Limited | Transport & logistics | 2024 |
| Cueto Consulting Ltd | Professional & scientific | 2018 |
| Culinary Craft Ltd | Hospitality | 2024 |
| Culinary Solutions International Ltd | Professional & scientific | 2020 |
| Cullmc & Sons Construction Ltd | Construction | 2026 |
| Culture LAB Consultancy Ltd | Professional & scientific | 2019 |
| Cupola Apartments Limited | Households | 2002 |
| Curaliving Ltd | Administrative & support | 2016 |
| Curantia Limited | Administrative & support | 2026 |
| Curate Living Limited | Professional & scientific | 2025 |
| Curate Staging & Design Studio Shop Ltd | Wholesale & retail | 2024 |
| Cure and Preserve Ltd | Construction | 2017 |
| Curio Haven Ltd | Wholesale & retail | 2025 |
| Curious APE Limited | Information & communication | 2008 |
| Curious Cat Productions Ltd | Information & communication | 2026 |
| Curlew Research Ltd | Information & communication | 2014 |
| Currency Matters Limited | Financial services | 2002 |
| Curry Kitchen MK Ltd | Hospitality | 2025 |
| Curtis Family Investments | Financial services | 2022 |
| Curved Lines Ltd | Administrative & support | 2018 |
| Curved Solutions Ltd | Construction | 2018 |
| Curvic Ltd | Professional & scientific | 2026 |
| Curvick Limited | Wholesale & retail | 2021 |
| CUS Property Investments Ltd | Real estate | 2024 |
| Cusca Estates Ltd | Real estate | 2025 |
| Cush Furniture Ltd | Wholesale & retail | 2022 |
| Custodian QA Ltd. | Professional & scientific | 2014 |
| Custom Boxes Wholesale Ltd | Manufacturing | 2024 |
| Custom Glaze (MK) Limited | Construction | 2018 |
| Custom Guards Ltd | Manufacturing | 2009 |
| Custom Heating & Plumbing Solutions Ltd | Construction | 2026 |
| Custom Heating and Plumbing LLP | | 2021 |
| Custom Renewables Ltd | Construction | 2022 |
| Custombus Limited | Financial services | 2020 |
| Customglaze Limited | Construction | 2006 |
| Customizex Ltd | Professional & scientific | 2023 |
| Custompress Ltd | Manufacturing | 2026 |
| Cute Dees Ltd | Health & social care | 2022 |
| Cute Maps Ltd | Arts & recreation | 2012 |
| Cutiolly Co., Ltd | Extraterritorial | 2026 |
| Cutler Associates Ltd | Professional & scientific | 2010 |
| Cuttermans Ltd | Other services | 2024 |
| Cutting Edge Consulting Ltd | Professional & scientific | 2025 |
| Cuttle Construction Ltd | Construction | 2000 |
| Cuttlebrook KOI Farm Limited | Agriculture & fishing | 2000 |
| CV Consulting (Design, MFG, ENG & Prof Recruitment) Ltd | Professional & scientific | 2019 |
| CV Energy Systems Ltd | Construction | 2025 |
| CV Wellbeing Limited | Health & social care | 2017 |
| Cventive Limited | Professional & scientific | 2002 |
| Cvirgo Limited | Health & social care | 2021 |
| Cvisions Studios Ltd | Arts & recreation | 2025 |
| CVL Holding Ltd | Financial services | 2020 |
| CW Complete Services Ltd | Administrative & support | 2026 |
| Cward Ltd | Administrative & support | 2026 |
| Cwez Properties Limited | Real estate | 2023 |
| CWP Design Limited | Other services | 2018 |
| Cwrt Pegasus RTM Company Limited | Households | 2025 |
| CWS Consulting Limited | Administrative & support | 2017 |
| CWS Hold Co Limited | Energy | 2015 |
| CXM Consulting Limited | Professional & scientific | 2001 |
| CXO Ltd | Wholesale & retail | 2017 |
| Cyber Deal Limited | Other services | 2021 |
| Cyber Defense Ltd | Information & communication | 2012 |
| Cyber Informatics Ltd | Information & communication | 2023 |
| Cyber Mentors & Consultants Ltd | Information & communication | 2023 |
| Cyber Smoke Infotech Ltd | Administrative & support | 2010 |
| Cyberapps Ltd | Information & communication | 2022 |