| Cleanpoint Building Services Limited | Construction | 2017 |
| Cleardene Solutions Ltd | Construction | 2019 |
| Clearscan Imaging Ltd | Health & social care | 2026 |
| Clever Heating Ltd | Construction | 2020 |
| Cleves Management Company (Sutton) Limited | Households | 1987 |
| CLG Property Services Ltd | Real estate | 2023 |
| Clickit London Limited | Manufacturing | 2014 |
| Climate Labs Ltd | Information & communication | 2017 |
| Climbstone Ltd | Real estate | 2025 |
| Cliniplan Ltd | Wholesale & retail | 2008 |
| Clinitools Limited | Education | 2024 |
| Clique 187 Ltd. | Real estate | 2021 |
| Clitheroe Property Management RTM Company Limited | Real estate | 2006 |
| Clive Bailey Limited | Health & social care | 2005 |
| Clock & Clock Ltd | Transport & logistics | 2024 |
| Clonlea Limited | Professional & scientific | 2023 |
| Cloud First Consulting Ltd | Information & communication | 2014 |
| Cloud Janus Ltd | Information & communication | 2020 |
| Cloud Tax Advisors Ltd | Professional & scientific | 2018 |
| Cloudathena Property Ltd | Real estate | 2022 |
| Cloudbiz Solutions Limited | Information & communication | 2018 |
| Cloudfit Enterprise Limited | Other services | 2022 |
| Cloudnine IT Services Ltd | Construction | 2015 |
| Cloudocity Limited | Real estate | 2020 |
| Cloudops Tech Ltd | Information & communication | 2026 |
| Cloudticks Ltd | Information & communication | 2013 |
| Clover Consultancy Limited | Administrative & support | 2019 |
| Clover Global Logistics Limited | Transport & logistics | 2019 |
| Clover IT Services Limited | Information & communication | 2019 |
| Clover Managed Services Limited | Administrative & support | 2019 |
| Clover Packaging Ltd | Administrative & support | 2022 |
| Clover Warehouse and Distribution Limited | Transport & logistics | 2019 |
| Club & Co. Events Limited | Hospitality | 2025 |
| Club Kenley Ltd | Administrative & support | 2022 |
| Clubpro (GK) Solutions Limited | Wholesale & retail | 2024 |
| CMK Health Solutions Ltd | Professional & scientific | 2025 |
| CN Healthcare Ltd | Health & social care | 2015 |
| Co-Efficient (Cheam) Limited | Professional & scientific | 2009 |
| Coach Rafaz Limited | Wholesale & retail | 2025 |
| Coastal Eagles Production Ltd | Health & social care | 2023 |
| Coated Screens Ltd | Administrative & support | 2019 |
| Cobalt Mercantile Ltd | Wholesale & retail | 2025 |
| Cocos Hair Ltd | Other services | 2024 |
| Code Effect Limited | Information & communication | 2017 |
| Codeseed Limited | Information & communication | 2015 |
| Codesense Solutions Ltd | Information & communication | 2024 |
| Cognihex Limited | Information & communication | 2025 |
| Coinbuild Limited | Construction | 1983 |
| Coke Elite Chauffeur Solutions Limited | Transport & logistics | 2022 |
| Coleridge Management (Sutton) Limited | Households | 2012 |
| Collab Services Ltd | Health & social care | 2020 |
| Collab Talent Solutions Limited | Administrative & support | 2024 |
| Collective Discovery Limited | Professional & scientific | 2020 |
| Collis & Russell Construction Ltd | Construction | 2022 |
| Colour Glazed Ltd | Construction | 2012 |
| Coluz Property Investment Company Ltd | Real estate | 2021 |
| Colva Consulting Limited | Professional & scientific | 2013 |
| Comberbrown Ltd | Construction | 2021 |
| Comfee Limited | Real estate | 2007 |
| Commercial & Domestic Solutions Ltd | Construction | 2012 |
| Commercial Domestic Services Ltd | Construction | 2021 |
| Community Action Sutton | Information & communication | 1997 |
| Community Hubs Sutton C.I.C. | Wholesale & retail | 2023 |
| Comon Network Limited | Administrative & support | 2008 |
| Compass Business Ltd | Real estate | 2015 |
| Compass Point Consulting Ltd | Professional & scientific | 2024 |
| Complete Financial Fitness Ltd | Financial services | 2005 |
| Complete Property Care (Southern) Limited | Administrative & support | 2011 |
| Complete Recruitment Services Ltd | Administrative & support | 2017 |
| Complete Services London Ltd | Construction | 2018 |
| Complete Sorting Solutions Limited | Transport & logistics | 2025 |
| Complex Fire Solutions Ltd | Construction | 2024 |
| Computer Intellects Limited | Information & communication | 2013 |
| Comvertex Limited | Professional & scientific | 2023 |
| Concept Golf Ltd | Information & communication | 2021 |
| Concept UK S & S Ltd | Wholesale & retail | 2018 |
| Concept Waste Management Limited | Water & waste | 2013 |
| Concerto Engineering Consultancy UK Ltd. | Professional & scientific | 2012 |
| Concho Ltd | Wholesale & retail | 2025 |
| Confessions of a Traitor Ltd | Arts & recreation | 2021 |
| Confidence Consulting Ltd | Financial services | 2022 |
| Confidence Cosmetics UK Ltd | Health & social care | 2016 |
| Connecting Bird Ltd | Administrative & support | 2019 |
| Connective Technologies Consulting Limited | Information & communication | 2021 |
| Connexum Limited | Professional & scientific | 2020 |
| Connieluscious Ltd | Other services | 2024 |
| Conscious Concepts Ltd | Manufacturing | 2019 |
| Consero Court (Surbiton) Management Company Limited | Real estate | 2006 |
| Consero Court (Sutton) Management Company Limited | Households | 2007 |
| Console Consultancy Ltd | Health & social care | 2013 |
| Consolidated Archive Holdings Limited | Arts & recreation | 2017 |
| Constance Retail Ltd | Wholesale & retail | 2022 |
| Constant Build Ltd | Construction | 2014 |
| Construct Builders Ltd | Construction | 2020 |
| Consult a Builder Ltd | Wholesale & retail | 2017 |
| Consulting Block Ltd | Information & communication | 2019 |
| Content Accelerator Group Limited | Wholesale & retail | 2025 |
| Contiem Holdings UK Limited | Information & communication | 1997 |
| Contiem Limited | Information & communication | 1990 |
| Conversorum Ltd | Information & communication | 2013 |