| Colin Harris Holdings Limited | Financial services | 2019 |
| Colin Wilks & Co. Limited | Professional & scientific | 2003 |
| Collabdev Solutions Ltd | Information & communication | 2025 |
| COLLABORATE.C8 Ltd | Professional & scientific | 2023 |
| Collaborative International Pesticides Analytical Council Ltd (the) | Professional & scientific | 1970 |
| Collard Consultancy Limited | Professional & scientific | 2023 |
| Collective Decisions Ltd | Financial services | 2002 |
| Collectives by Curated Ltd | Hospitality | 2026 |
| Collectíf Limited | Information & communication | 2023 |
| College Mansions Management Limited | Households | 1997 |
| College of Integrative Medicine Ltd | Public administration | 2025 |
| College of VCP Limited | Education | 2019 |
| Collettelectrical Limited | Construction | 2026 |
| Collicopia Limited | Wholesale & retail | 2025 |
| Collins Home Services Ltd | Administrative & support | 2018 |
| Collision Management Systems Limited | Information & communication | 2012 |
| Collums Solutions Limited | Information & communication | 2018 |
| Colman & Rose Limited | Administrative & support | 2023 |
| Colmore Projects Limited | Construction | 2025 |
| Colmount Holdings Limited | Financial services | 2020 |
| Colmount Ltd | Professional & scientific | 2019 |
| Colmount Property Limited | Real estate | 2020 |
| Colney Manor Resident Management Company Limited | Households | 2023 |
| Colombo Edition (Crewe) Limited | Hospitality | 2025 |
| Colombo Edition (Warwick) Limited | Hospitality | 2025 |
| Colosseum Consulting Ltd | Professional & scientific | 2015 |
| Colourful Cleaning Services MK Limited | Administrative & support | 2020 |
| Colourful Healthcare Solutions Ltd | Health & social care | 2023 |
| Colourtone Powder Coaters Limited | Manufacturing | 2002 |
| Colt Press Limited | Manufacturing | 2007 |
| Columbas Homes Limited | Real estate | 2019 |
| Colville Capital Partners Limited | Financial services | 2012 |
| Combat Zone Willen Lake Ltd | Arts & recreation | 2025 |
| Combicat Ltd | Manufacturing | 2013 |
| Combined Independents (Bedfordshire & Northamptonshire)Limited | Wholesale & retail | 1967 |
| Comedy Club Technology Ltd | Information & communication | 2025 |
| Comel Bellway Cbst Limited | Wholesale & retail | 2026 |
| Comet Security Services Ltd | Administrative & support | 2021 |
| Comformit Solutions Limited | Information & communication | 2013 |
| Comfort Floors Limited | Construction | 2017 |
| Comfort Living Care Services Ltd | Health & social care | 2020 |
| Comfort Memorial Food for ALL | Hospitality | 2015 |
| Comfort Scan Limited | Health & social care | 2025 |
| Comfort Solutions Limited | Wholesale & retail | 2014 |
| Comfort Waves Ltd | Wholesale & retail | 2020 |
| Comfortable Adventure Limited | Transport & logistics | 2025 |
| Comforter Healthcare Limited | Health & social care | 2021 |
| Comfy Feet Limited | Health & social care | 2025 |
| Comfy Leisure Ltd | Hospitality | 2024 |
| Comfy Technest Ltd | Wholesale & retail | 2024 |
| Comfygo Ltd | Wholesale & retail | 2025 |
| Commence AI Limited | Information & communication | 2023 |
| Commerce Pulse Ltd. | Information & communication | 2017 |
| Commercial Automotive Rentals Ltd | Administrative & support | 2023 |
| Commercial Data Limited | Information & communication | 2018 |
| Commercial Law Solutions Limited | Professional & scientific | 2014 |
| Commex Limited | Financial services | 2006 |
| Commitment Cleaning Limited | Administrative & support | 2025 |
| Committed Solutions Ltd | Transport & logistics | 2020 |
| Commodities Trading Limited | Wholesale & retail | 1999 |
| Commply (Yorkshire) Limited | Wholesale & retail | 2003 |
| Communicate Moore Ltd | Professional & scientific | 2026 |
| Community Action: MK | Other services | 2001 |
| Community Arts Resource Centre CIC | Arts & recreation | 2009 |
| Community Commodities Limited | Professional & scientific | 2017 |
| Community Development and Training Ltd | Hospitality | 2025 |
| Community Outreach and Liaison Support CIC | Other services | 2025 |
| Community Solutions UK Limited | Hospitality | 2007 |
| Community Trust Network | Administrative & support | 2012 |
| Comodius Capital Ltd | Financial services | 2023 |
| Companion Connect Ltd | Health & social care | 2025 |
| Company of Nature Ltd | Professional & scientific | 2021 |
| COMPANY-91 Limited | Information & communication | 2019 |
| Compare Tiled Conservatory Roofs Limited | Information & communication | 2018 |
| Compass Construction MK Ltd | Real estate | 2025 |
| Compass Point (ST Ives) Management Company Limited | Real estate | 2001 |
| Compass Roofing and Building Ltd | Construction | 2019 |
| Compassion Circle CIC | Administrative & support | 2026 |
| Complete Access Systems Ltd | Administrative & support | 2010 |
| Complete Build Construction Limited | Construction | 2012 |
| Complete Cleaning (Bucks and Beds) Limited | Administrative & support | 2023 |
| Complete Electronics Holdings Ltd | Financial services | 2026 |
| Complete Electronics Limited | Manufacturing | 2006 |
| Complete Event Security Ltd | Administrative & support | 2024 |
| Complete Management Services Ltd | Other services | 2016 |
| Completely Content Ltd. | Arts & recreation | 2015 |
| Complex Care MK Ltd | Health & social care | 2021 |
| Complex Systems Digital Campus Limited | Professional & scientific | 2014 |
| Comply Vault Ltd | Information & communication | 2026 |
| Complyfox Ltd | Information & communication | 2019 |
| Component Creations Limited | Manufacturing | 2013 |
| Compositis Consulting Limited | Professional & scientific | 2022 |
| Comprehensive Services Ltd | Professional & scientific | 2016 |
| Compressed Air Technologies Ltd | Manufacturing | 2008 |
| Computamation Services Limited | Information & communication | 1998 |
| Computamation Systems Limited | Information & communication | 1985 |
| Computer Remarketing Services Limited | Information & communication | 1980 |
| Computer Systems Analysts Limited | Information & communication | 2011 |
| Comsis Ltd | Information & communication | 2020 |
| Comtec Business Computing Limited | Information & communication | 1993 |