| COL Financial Services Ltd. | Other services | 2014 |
| Colben Limited | Agriculture & fishing | 1996 |
| Colby Driving Ltd | Transport & logistics | 2007 |
| Colby Engineering Ltd | Professional & scientific | 2025 |
| Colby Holdings Limited | Financial services | 2022 |
| Colby Investments Limited | Real estate | 2019 |
| Cold Stores Holdings Limited | Financial services | 2019 |
| Coldascript Limited | Administrative & support | 2012 |
| Coleman Build (Northampton) Ltd | Construction | 2016 |
| Coles Elevate Ltd | Professional & scientific | 2025 |
| Colin Hood - SE Limited | Real estate | 2013 |
| Colin Hood Property Limited | Real estate | 2016 |
| Colin Ross Photography Ltd | Professional & scientific | 2022 |
| Collectemall Limited | Arts & recreation | 2024 |
| Collectible Watches Ltd | Wholesale & retail | 2026 |
| Collection POT Holdings Limited | Financial services | 2022 |
| Collection POT Limited | Wholesale & retail | 2017 |
| Collection POT Technology Limited | Financial services | 2024 |
| College Mews Management (Kettering) Limited | Administrative & support | 1984 |
| College Street Management Limited | Administrative & support | 2010 |
| Collingtree Build Limited | Construction | 2022 |
| Collingtree Carpentry Ltd | Construction | 2024 |
| Collingtree Consultancy Limited | Professional & scientific | 2013 |
| Collingtree Enterprises Limited | Professional & scientific | 2003 |
| Collingtree Financial Limited | Financial services | 2006 |
| Collingtree Ltd | Real estate | 2010 |
| Collins & Sons Haulage Ltd | Transport & logistics | 2021 |
| Collins and George Property Investments Ltd | Administrative & support | 2026 |
| Collins Fresh Produce Ltd | Wholesale & retail | 1975 |
| Collis Castrum Limited | Administrative & support | 2006 |
| Collow Properties Limited | Real estate | 2021 |
| Colombiano KRS Ltd | Hospitality | 2026 |
| Color Secret UK Ltd | Professional & scientific | 2019 |
| Colormove Transport Limited | Wholesale & retail | 2025 |
| Colorphaze Limited | Manufacturing | 1988 |
| Colors Transport Ltd | Transport & logistics | 2021 |
| Colourfully Engaged Ltd | Education | 2011 |
| Colston Bassett School Limited | Education | 2007 |
| Colwyn Road 63 Management Company Limited | Hospitality | 1993 |
| Coman Service Ltd | Wholesale & retail | 2025 |
| Combat-Gardening-Services Ltd | Professional & scientific | 2026 |
| Combi Nation Solution Ltd | Other services | 2009 |
| Combined Facilities Solutions Ltd | Administrative & support | 2012 |
| Combisafe International Limited | Construction | 1993 |
| Comercia Equipment Sales Limited | Extraterritorial | 1991 |
| Comfea Limited | Wholesale & retail | 2025 |
| Comfort Coaches Transport Ltd | Transport & logistics | 2025 |
| Comfort Option Limited | Administrative & support | 2014 |
| Comgenial Ltd | Wholesale & retail | 2023 |
| Comm Solve Solutions Limited | Construction | 2015 |
| Commagility Holdings Ltd | Financial services | 2017 |
| Commagility Limited | Manufacturing | 2006 |
| Commercial Equipment Solutions Limited | Wholesale & retail | 2024 |
| Commercial Fire Limited | Public administration | 2025 |
| Commercial IT Ltd | Information & communication | 2021 |
| Commercial Panels and Pressings Ltd. | Manufacturing | 2015 |
| Commercial Panels Limited | Extraterritorial | 2015 |
| Commercial Pressings & Panels Limited | Extraterritorial | 2015 |
| Commercial Street (Higham) Limited | Households | 2012 |
| Commercial Transport Ltd | Transport & logistics | 2023 |
| Commercial Vehicle Bodies (Northampton) Limited | Manufacturing | 2019 |
| Commodity Trading Limited | Professional & scientific | 1992 |
| Common Laser Technologies Limited | Professional & scientific | 2026 |
| Common Unity Wellbeing Ltd | Health & social care | 2024 |
| Commonwealth Organisation for Social Work | Other services | 2005 |
| Commonwealth Produce Ltd | Wholesale & retail | 2018 |
| Commpower Limited | Information & communication | 2007 |
| Commtek (UK) Limited | Information & communication | 2000 |
| Communication Edge Ltd | Information & communication | 2019 |
| Community EAR Health Ltd | Health & social care | 2026 |
| Community Law Service (Northampton and County) | Professional & scientific | 2009 |
| Community Links Services Ltd | Education | 2008 |
| Community Spaces Northampton | Hospitality | 2011 |
| Community Support Training Ltd | Professional & scientific | 2022 |
| Company AI Solutions Limited | Administrative & support | 2026 |
| Compass Health UK Limited | Health & social care | 2024 |
| Compass Healthcare Limited | Professional & scientific | 2015 |
| Compass IT Services Ltd | Information & communication | 2020 |
| Compassionate Social Care Ltd. | Health & social care | 2015 |
| Competitive Edge Training and Consultancy Limited | Administrative & support | 2017 |
| Complete Autocare Limited | Wholesale & retail | 2004 |
| Complete Catering Projects Ltd | Manufacturing | 2021 |
| Complete Civil Engineering & Construction Ltd | Construction | 2018 |
| Complete Drawers Solution Ltd | Manufacturing | 2019 |
| Complete Electrical Installations (Midlands) Ltd | Construction | 2022 |
| Complete Exterior Cleaning Limited | Administrative & support | 2023 |
| Complete Flooring Services Limited | Construction | 2018 |
| Complete Homes (Midlands) Limited | Construction | 2006 |
| Complete Move Solutions Limited | Households | 2017 |
| Complete People Solutions Ltd | Health & social care | 2019 |
| Complete Safety Systems Limited | Manufacturing | 2003 |
| Complete Solar Installations (Midlands) Ltd | Construction | 2025 |
| Complete Steel Fabrications Ltd | Construction | 2017 |
| Complete Stoves Ltd | Wholesale & retail | 2023 |
| Complete Support Care Services Limited | Health & social care | 2018 |
| Complete Turnkey Engineering Limited | Professional & scientific | 2023 |
| Completely Cleaning (Northants) Ltd | Administrative & support | 2026 |
| Complink Homes Limited | Real estate | 2022 |
| Complyra Limited | Professional & scientific | 2025 |
| Compound Electrical Limited | Construction | 1967 |