| Continental Property Networks Limited | Real estate | 2023 |
| Control Systems Technology Limited | Professional & scientific | 2017 |
| Convex Energy Limited | Energy | 2018 |
| Cook-Gray Property Holdings Ltd | Real estate | 2022 |
| Cook-Gray Property Partnership LLP | | 2022 |
| Copied Right Limited | Manufacturing | 2021 |
| Copperlink Homes Limited | Real estate | 2024 |
| Copperlink Ltd | Construction | 2021 |
| Coqual Limited | Education | 2024 |
| Core EX Limited | Professional & scientific | 2026 |
| Core Structural Limited | Professional & scientific | 2021 |
| Corner Plot Properties Ltd | Real estate | 2020 |
| Cosco Wholesale UK Ltd | Wholesale & retail | 2025 |
| Cosmar Limited | Information & communication | 2004 |
| Cosmar Partners LLP | | 2016 |
| Cosmar Properties Ltd | Real estate | 2012 |
| Cosmolab Manufacturing Ltd | Health & social care | 2010 |
| Covol Engineering Limited | Professional & scientific | 2018 |
| Cowans Commercial Ltd | Construction | 2024 |
| Cowpen Industrial Association (BID) Limited | Administrative & support | 2007 |
| Cowpen Lane Convenience Store Limited | Wholesale & retail | 2020 |
| Cp&G Ltd | Professional & scientific | 2025 |
| CPM E&I Limited | Professional & scientific | 2026 |
| CR Wealth Management Limited | Financial services | 2012 |
| Crafty Cock PUB Company Limited | Hospitality | 2017 |
| Craggs Psychology Limited | Health & social care | 2025 |
| Craven Enterprises Limited | Health & social care | 2014 |
| Creating Confident Smiles Ltd | Health & social care | 2023 |
| Creative 9 and Partners LLP | | 2020 |
| Crest Payroll Limited | Administrative & support | 2019 |
| Crews Associates Limited | Real estate | 2004 |
| Crews Family Partnership LLP | | 2023 |
| Crime Academy Limited | Extraterritorial | 2024 |
| Crjm Limited | Mining & quarrying | 2014 |
| CRK Property Group Ltd | Real estate | 2022 |
| CRM Health and Fitness Ltd | Arts & recreation | 2020 |
| Crowdy Family Partnership LLP | | 2020 |
| Crystal Cloud Services Ltd | Information & communication | 2026 |
| CS Enterprises Ltd | Hospitality | 2016 |
| CSE & I Housing Ltd | Real estate | 2019 |
| Cullen Legal Limited | Professional & scientific | 2013 |
| Curious Combination Limited | Other services | 2014 |
| Curtis Family Holdings Ltd | Real estate | 2022 |
| Curtis Family Partnership LLP | | 2022 |
| Curtis Plumbing & Heating (NE) Ltd | Construction | 2021 |
| Cutler & Maclean Limited | Manufacturing | 1979 |
| Cutting Edge Buckets Limited | Other services | 2017 |
| CWJ Property Ltd | Real estate | 2023 |
| Cyott Partnership LLP | | 2018 |
| CZ Event Management Limited | Administrative & support | 2019 |
| D & DC Construction Limited | Professional & scientific | 2022 |
| D & M Rapaport Limited | Wholesale & retail | 2008 |
| D & R Motors (Billingham) Limited | Wholesale & retail | 2015 |
| D Johnson Homes Limited | Real estate | 2025 |
| D L Miller Haulage Limited | Transport & logistics | 2005 |
| D Lane Builders Limited | Construction | 2022 |
| D Leyden Developments Ltd | Construction | 2011 |
| D P Solutions N E Limited | Extraterritorial | 2014 |
| D&E Munro WP Ltd | Administrative & support | 2024 |
| D-M-A Accountancy Limited | Professional & scientific | 2023 |
| D.R. Caswell Limited | Wholesale & retail | 1972 |
| Daily Maid (Teesside) Limited | Administrative & support | 2024 |
| Daisy for Diagnostic Services Ltd | Health & social care | 2023 |
| Damz Products Ltd | Wholesale & retail | 2026 |
| Dana & Farah Limited | Health & social care | 2025 |
| Dancing in the Rain Ltd | Health & social care | 2024 |
| Darby Family Partnership LLP | | 2019 |
| Darbytech Limited | Manufacturing | 2017 |
| Darley Homes Estates Limited | Real estate | 2017 |
| Data Centre Cabling Ltd | Manufacturing | 2024 |
| Dattani Family Partnership LLP | | 2021 |
| David Cody Fabrications Ltd | Manufacturing | 2019 |
| David Cone Consulting Ltd | Professional & scientific | 2017 |
| David H Limited | Financial services | 2026 |
| David Lowrie Design Solutions Ltd | Professional & scientific | 2011 |
| Davison Builders Ltd | Construction | 2018 |
| Dazley Limited | Professional & scientific | 2012 |
| DB Technical Consultants Limited | Professional & scientific | 2014 |
| DBE Inspection Limited | Construction | 2018 |
| DC GAS Service and Repair Ltd | Construction | 2022 |
| DC Instruments Ltd | Professional & scientific | 2024 |
| DCF Consulting Ltd | Professional & scientific | 2023 |
| DCS Pharar Ltd | Real estate | 2018 |
| DDP Properties LLP | | 2019 |
| DDT Homes Ltd | Real estate | 2020 |
| Dedar Northeast Ltd | Other services | 2019 |
| Deengineered Limited | Professional & scientific | 2021 |
| Defect Doctor Limited | Construction | 2020 |
| Dekarbonize Ltd | Professional & scientific | 2020 |
| Delaphesport Ltd | Wholesale & retail | 2024 |
| Delilah BO GEL Nails Ltd | Other services | 2019 |
| Delirilium Properties Ltd | Real estate | 2025 |
| Delma Homes Ltd | Real estate | 2014 |
| Delta Coaches Limited | Transport & logistics | 2002 |
| Den-E-Lee (Poultry) Limited | Manufacturing | 2014 |
| Denovo Property (North East) Ltd | Real estate | 2017 |
| Dentirad Limited | Health & social care | 2026 |
| Dermmed Aesthetics Limited | Health & social care | 2023 |
| DES Carpets Ltd | Construction | 2025 |
| Desai Family Holdings Limited | Real estate | 2018 |