| Clickable Media Limited | Information & communication | 2015 |
| Clinical Psychology Consultants Limited | Health & social care | 2011 |
| Cliniqcraft Limited | Information & communication | 2026 |
| CLM Kind Hands Care Services Limited | Health & social care | 2026 |
| Cloud and Pixel Limited | Information & communication | 2018 |
| Cloudcitygaming Ltd | Wholesale & retail | 2018 |
| CLS Electrical Services Ltd | Construction | 2020 |
| Cluck Collective Ltd | Hospitality | 2025 |
| Coal and Clay Connections CIC | Administrative & support | 2025 |
| Coffee Cruise Ltd | Wholesale & retail | 2025 |
| Coiled Blue Limited | Construction | 2015 |
| Coker and Sons Ltd | Manufacturing | 2024 |
| Coley Property Services Limited | Real estate | 2016 |
| Coley Thomson Limited | Real estate | 2004 |
| Colocation Park Limited | Information & communication | 2019 |
| Colour Sparks Therapy Ltd | Other services | 2018 |
| Comet Electricals Limited | Wholesale & retail | 2021 |
| Commerce Windows Limited | Construction | 2003 |
| Commminibus Limited | Transport & logistics | 2020 |
| Community Training Solutions Limited | Education | 2022 |
| Compass Care and Consultancy Limited | Professional & scientific | 2024 |
| Compass Cars 247 Limited | Transport & logistics | 2009 |
| Compass Construction Projects Limited | Construction | 2024 |
| Compiforce Limited | Information & communication | 1985 |
| Consbud Ltd | Construction | 2025 |
| Contalex Ltd | Professional & scientific | 2022 |
| Contractor Power Ltd | Transport & logistics | 2025 |
| Controls-Services Ltd | Manufacturing | 2012 |
| Core Health Staffing Limited | Administrative & support | 2025 |
| Coretrade Wholesale Ltd | Wholesale & retail | 2026 |
| Cornerstone Build and Developments Ltd | Construction | 2026 |
| Corpus Conditioning Limited | Administrative & support | 2026 |
| Coulson Real Estate Ltd | Real estate | 2023 |
| Countersales UK Limited | Extraterritorial | 2002 |
| County Fire Services Limited | Construction | 2008 |
| County Power Limited | Construction | 2006 |
| Courtney's Exterior Cleaning Ltd | Other services | 2019 |
| CP CBD Ltd | Wholesale & retail | 2021 |
| CPI Data Ltd | Construction | 2025 |
| CPI Engineering Ltd | Other services | 2024 |
| CPI Trading Group Ltd | Professional & scientific | 2025 |
| CRA Property Management Limited | Real estate | 2025 |
| Cranford Ironstone Company Ltd | Construction | 2025 |
| Crestline Investments Ltd | Real estate | 2023 |
| Cretu Trans Ltd | Transport & logistics | 2018 |
| Critterkiller Pest Control Ltd | Agriculture & fishing | 2019 |
| Crockett Data Solutions Ltd | Information & communication | 2025 |
| Cromer Beach Treats Ltd | Hospitality | 2023 |
| Crook Properties Ltd | Real estate | 2024 |
| Crown Park (Rushden) Limited | Real estate | 2010 |
| Crown Rooms Limited | Construction | 2022 |
| Crowthorpe Investments Ltd | Real estate | 2019 |
| Cruise Limited | Extraterritorial | 1993 |
| Crystal Village Ltd | Hospitality | 2022 |
| CS Company Secretaries Ltd | Households | 2021 |
| CSR Digital Limited | Manufacturing | 2004 |
| CTE Productions Limited | Wholesale & retail | 2006 |
| Curran Heating Limited | Construction | 2019 |
| Custodian Fire & Security Ltd | Administrative & support | 2018 |
| Custom-Clothing.Xyz Ltd | Wholesale & retail | 2023 |
| Cutting Systems UK Ltd | Manufacturing | 2001 |
| Cynosura Consulting Ltd | Professional & scientific | 2015 |
| D Francis Services Ltd | Transport & logistics | 2022 |
| D S Builders (Northants) Ltd | Construction | 2018 |
| D&A Buy to LET Ltd | Real estate | 2023 |
| D&K Consultancy Ltd | Information & communication | 2025 |
| D&L Electrical & Fire Protection Ltd | Construction | 2016 |
| D&M Caushaj Ltd | Real estate | 2024 |
| D-Line Roofing Ltd | Construction | 2021 |
| D.Balauta Ltd | Manufacturing | 2019 |
| D.J.M. Technical Limited | Information & communication | 2007 |
| D.R.W. & Sons Limited | Wholesale & retail | 2008 |
| Daisy Living Services Ltd | Health & social care | 2020 |
| Daks Developments Ltd | Construction | 2022 |
| Daks Property 2 Ltd | Real estate | 2022 |
| Daks Property 3 Ltd | Real estate | 2025 |
| Daks Property Ltd | Real estate | 2017 |
| Damlog Ltd | Transport & logistics | 2022 |
| DAN Home Serve Limited | Wholesale & retail | 2023 |
| Danavic Construction Ltd | Construction | 2021 |
| Daniel Hewitt Bathroom & Plumbing Services Limited | Construction | 2023 |
| Danmacfitness Ltd | Other services | 2019 |
| Darich Homes (Northants) Limited | Construction | 2019 |
| Darien Property Services Ltd | Construction | 2018 |
| Dariens Property Maintenance Limited | Construction | 2022 |
| Darlo Care Ltd | Health & social care | 2010 |
| Darren Lucas Plastering Ltd. | Construction | 2005 |
| Darren Stevens Limited | Education | 2024 |
| Datacentres Recare Limited | Wholesale & retail | 2018 |
| Dataworxs.Net (Northamptonshire) Ltd | Administrative & support | 2019 |
| Davard Developments Limited | Construction | 1990 |
| Davelyn Construction Ltd | Construction | 2024 |
| David Millwood Supplies Ltd | Wholesale & retail | 2018 |
| David Moon Limited | Professional & scientific | 2011 |
| David Tobias Cook Limited | Administrative & support | 2013 |
| David Whiting Properties Limited | Real estate | 2022 |
| David Whiting Solutions Limited | Construction | 2014 |
| Dayeblake Limited | Wholesale & retail | 2025 |
| DAZ B Transport Ltd | Transport & logistics | 2021 |
| DB Automotive Vehicle Solutions Ltd | Wholesale & retail | 2023 |