| Concept CAD Limited | Administrative & support | 2005 |
| Concept Clinics Healthcare Limited | Health & social care | 2011 |
| Concept Floor Screeds Ltd | Construction | 2024 |
| Concept Furniture Group Ltd | Manufacturing | 2021 |
| Concept Legum Ltd | Wholesale & retail | 2022 |
| Concept Liquids Limited | Wholesale & retail | 2012 |
| Concept Living Entertainment Limited | | 2012 |
| Concept Painting Contractors Limited | Construction | 2000 |
| Concept Wills Limited | Administrative & support | 2017 |
| CONCEPT2MARKET Limited | Extraterritorial | 2006 |
| Concise Broadcasting Limited | Information & communication | 2021 |
| Concise Technologies Group Limited | Financial services | 2008 |
| Concise Technologies Limited | Information & communication | 1999 |
| Concise Web Design Limited | Professional & scientific | 2003 |
| Concoll Limited | Real estate | 2017 |
| Concord Machinery Limited | Administrative & support | 2026 |
| Concord Rise Group Ltd | Construction | 2025 |
| Concorde and Wilson Limited | Real estate | 2014 |
| Concorde Interiors (Design & Build) Limited | Real estate | 1998 |
| Concordia Music Ltd | Education | 2014 |
| Concrete Panel Limited | Manufacturing | 2012 |
| CONCRETE4CHANGE Ltd | Manufacturing | 2021 |
| Concur | Wholesale & retail | 1963 |
| Concussion Rebalanced Ltd | Health & social care | 2020 |
| Conder Small Projects Limited | Professional & scientific | 2008 |
| Conduit Fencing (Lincoln) Limited | Construction | 2017 |
| Coneybeare & Company Limited | Financial services | 1930 |
| Conferencehousing Limited | Administrative & support | 2020 |
| Confetti Constellations Limited | Manufacturing | 2005 |
| Confetti Media Limited | Education | 2015 |
| CONFID3NTIAL Ltd | Professional & scientific | 2021 |
| Confide Limited | Extraterritorial | 1995 |
| Confidence Rising Limited | Professional & scientific | 2025 |
| Confidence Uyi-Olaye Limited | Wholesale & retail | 2022 |
| Confident Caregivers Community Interest Company | Health & social care | 2026 |
| Congleton V.E. Limited | Other services | 2019 |
| Congregational Federation Limited(The) | Other services | 1974 |
| Conico Commercial Cleaning Limited | Administrative & support | 2015 |
| Conifers Rest Home Limited | Health & social care | 2005 |
| Conker Bespoke Furniture Limited | Manufacturing | 2017 |
| Conker Cloud Innovations Limited | Information & communication | 1989 |
| Connect Care Group Ltd | Administrative & support | 2025 |
| Connect Cars Nottingham Ltd | Transport & logistics | 2025 |
| Connect Counselling & Psychotherapy Ltd | Health & social care | 2023 |
| Connect UK 001 Ltd | Wholesale & retail | 2020 |
| Connect-Protect Ltd | Construction | 2016 |
| Connected Security Services Limited | Administrative & support | 2018 |
| Connected Systems Solutions Limited | Information & communication | 2013 |
| Connecting DYS CIC | Other services | 2025 |
| Connective Associates Ltd | Real estate | 2003 |
| Connective Properties Limited | Real estate | 2001 |
| Connecture Limited | Construction | 2015 |
| Connellan's Castles Ltd | Arts & recreation | 2026 |
| Connelly Invest Limited | Real estate | 2003 |
| Connex Logistics Ltd | Transport & logistics | 2024 |
| Connexiauk Ltd | Administrative & support | 2024 |
| Connexion International Ltd | Wholesale & retail | 2020 |
| Conniston Care Holdings Limited | Financial services | 2025 |
| Conniston Care Limited | Health & social care | 2006 |
| Connoisseurs IP Ltd | Information & communication | 2026 |
| Connoisseurs of Music CIC | Arts & recreation | 2026 |
| Connolly IT Services Limited | Information & communication | 2011 |
| Connolly Land & Developments Ltd | Real estate | 2008 |
| Connolly Vision (Holdings) Limited | Financial services | 2008 |
| Connor Rowden Ltd | Professional & scientific | 2025 |
| Conquer Cape Town Ltd. | Administrative & support | 2022 |
| Conquer Learning Ltd | Education | 2025 |
| Conquest Electrical Ltd | Construction | 2024 |
| Conquest Records Limited | Information & communication | 2020 |
| Conrads Building Contractors Limited | Construction | 2017 |
| Cons M Ltd | Construction | 2025 |
| Cons-Dino Ltd | Construction | 2025 |
| Consa Ltd | Health & social care | 2021 |
| Conscious Homes Ltd. | Real estate | 2016 |
| Conscious Homes Property Management Ltd | Real estate | 2017 |
| Consensus Commercial Management Limited | Professional & scientific | 2013 |
| Consensus Consultancy Ltd | Wholesale & retail | 2021 |
| Conserv-A-Clean Limited | Administrative & support | 2006 |
| Conservation+Restoration+Design Limited | Professional & scientific | 2011 |
| Conservatory Roof Conversions Limited | Construction | 2025 |
| Consilium Coaching Ltd | Other services | 2025 |
| Consistent Clothing Ltd | Wholesale & retail | 2019 |
| Consistent Key Ltd | Real estate | 2020 |
| Consolidated Utilities UK Ltd | Professional & scientific | 1997 |
| Consortia Network Limited | Administrative & support | 2004 |
| Consortium Collective Ltd | Real estate | 2025 |
| Constable & Smith Event Planning Limited | Administrative & support | 2004 |
| Constance Murray Ltd | Real estate | 2014 |
| Constant Pressure Ltd | Administrative & support | 2026 |
| Constant Recruitment Agency Ltd | Administrative & support | 2020 |
| Constantine Coporation Ltd | Construction | 2014 |
| Constantine Intelligence Ltd | Information & communication | 2026 |
| Constantinople Consultancy Ltd | Construction | 2019 |
| Constellate Ltd | Administrative & support | 2023 |
| Constellation Ltd | Wholesale & retail | 2024 |
| Constellation Solutions Ltd | Professional & scientific | 2025 |
| Construct 28 Limited | Construction | 2024 |
| Construction 9 Ltd | Construction | 2013 |
| Construction Art Ltd | Wholesale & retail | 2012 |
| Construction Design Solutions Limited | Professional & scientific | 2005 |