| CUBE4 Limited | Construction | 2018 |
| CUBE4 Property Limited | Real estate | 2019 |
| Cubeloid Solutions Ltd | Information & communication | 2018 |
| Cumbrian Industrials Limited | Professional & scientific | 1971 |
| Cummings Commercial Holdings Limited | Financial services | 2017 |
| Cummings Commercial Limited | Professional & scientific | 1997 |
| Cupcopper Ltd | Hospitality | 2018 |
| Cupertino Medical Ltd | Health & social care | 2023 |
| Curated Closet Preloved Fashion Ltd | Wholesale & retail | 2025 |
| Curated Curiosity Ltd | Arts & recreation | 2025 |
| Curlew and KIN Ltd | Professional & scientific | 2022 |
| Curls Lane Management Company Limited | Households | 2005 |
| Curo Facilities Services Limited | Administrative & support | 2024 |
| Curtis Recruitment Limited | Administrative & support | 2015 |
| Custdem Designs Ltd | Manufacturing | 2023 |
| Custom AV Distribution Limited | Wholesale & retail | 2008 |
| Custom Gaming Ltd | Manufacturing | 2025 |
| Custom House Windows Limited | Wholesale & retail | 2009 |
| Cutlers Close (Maidenhead) Management Company Limited | Households | 2016 |
| Cuvée Consultancy Ltd | Wholesale & retail | 2024 |
| Cvjlondon Limited | Professional & scientific | 2015 |
| CWR Property Ltd | Other services | 2019 |
| CWW TV and Media Limited | Information & communication | 2021 |
| CX Vantage Limited | Information & communication | 2023 |
| Cyber & Cloud Secops Ltd | Information & communication | 2024 |
| Cyber AI Line Limited | Information & communication | 2024 |
| Cyber Balance Ltd | Administrative & support | 2017 |
| Cyber Trooper Limited | Professional & scientific | 2015 |
| Cyberba Consulting Limited | Information & communication | 2022 |
| Cyberhash Limited | Information & communication | 2023 |
| Cyberyogi Ltd | Manufacturing | 2026 |
| Cybex Ventures Limited | Professional & scientific | 2011 |
| Cynsol Ltd | Wholesale & retail | 2022 |
| Cyprolics Limited | Information & communication | 2017 |
| Côte D’Azur Limited | Professional & scientific | 2018 |
| D & C Building Services Limited | Construction | 2004 |
| D & N Metal Limited | Manufacturing | 2010 |
| D and S Thompson Contractors Ltd | Agriculture & fishing | 2005 |
| D Heating Ltd | Construction | 2024 |
| D L S Developments Limited | Real estate | 2010 |
| D M Cager (Insurance Brokers) Limited | Financial services | 1970 |
| D M Cager Limited | Financial services | 2010 |
| D N Gardens Limited | Administrative & support | 2018 |
| D&E Kilpatrick Limited | Real estate | 2023 |
| D.B.S. CAD Services Limited | Professional & scientific | 2008 |
| D.I.C.E Electrical Ltd | Construction | 2019 |
| D.M.M. Consultancy Limited | Professional & scientific | 1991 |
| D.P. Slatter Ltd | Construction | 2021 |
| Daarc Ltd | Information & communication | 2026 |
| DAB Hands Delivery Ltd | Professional & scientific | 2026 |
| Dacorum Sports Trust | Arts & recreation | 2003 |
| Dadpals Limited | Information & communication | 2025 |
| Dahua Technology UK Limited | Administrative & support | 2016 |
| Dainton & Dainton Ltd | Construction | 2016 |
| Daisy DOT Creative Ltd | Arts & recreation | 2016 |
| Dallas News & Convenience Store Limited | Wholesale & retail | 2008 |
| Danbrit Property Limited | Real estate | 2002 |
| Dance Developments Beaconsfield Limited | Construction | 2026 |
| Dance Developments Limited | Construction | 2010 |
| Dance Parties Limited | Arts & recreation | 2012 |
| Dance Properties Ltd | Construction | 2022 |
| Dancing With ANT Ltd | Arts & recreation | 2024 |
| Dandelion Life Limited | Professional & scientific | 2014 |
| Daneli Consulting Limited | Information & communication | 2009 |
| Danes Court Residents Association (Maidenhead) Limited | Real estate | 1976 |
| Daniel & Company (Southern) Limited | Construction | 2010 |
| Daniel Kelly Painting and Decorating Limited | Construction | 2019 |
| Daniel Moore Fitness Ltd | Arts & recreation | 2026 |
| Dann Barbers Ltd | Other services | 2011 |
| DAP Group Limited | Financial services | 2019 |
| Dapper PUP Ltd | Wholesale & retail | 2025 |
| Dara Williams Limited | Professional & scientific | 2014 |
| Dark Blue Properties Limited | Construction | 2017 |
| Dark Horses Investments Ltd | Real estate | 2021 |
| Darlees Wind Farm Limited | Energy | 2022 |
| Darren Pickersgill Consultancy Ltd | Administrative & support | 2024 |
| Dart Resourcing Limited | Professional & scientific | 2022 |
| Data Insights Team Limited | Information & communication | 2024 |
| Data Service Consultants Limited | Information & communication | 1990 |
| Data Worldwide Limited | Professional & scientific | 1998 |
| Databanx Limited | Extraterritorial | 2003 |
| Databuzz Ltd | Information & communication | 2017 |
| Datahighway Limited | Other services | 2012 |
| Datchet Investments Limited | Construction | 2015 |
| Datta Recruitment Consulting Ltd | Administrative & support | 2022 |
| Dauncey Limited | Professional & scientific | 2012 |
| Davals Design Ltd | Manufacturing | 2025 |
| Davat Limited | Wholesale & retail | 2024 |
| David Guile Coaching Limited | Professional & scientific | 2015 |
| David Hindle Limited | Construction | 2015 |
| David Messum Fine Art Limited | Wholesale & retail | 1993 |
| Davidovitz Productions Limited | Information & communication | 2002 |
| Davies Estate Planning Limited | Professional & scientific | 2020 |
| Davies-Small Architects Ltd | Professional & scientific | 2025 |
| Dawes Electrical Services Limited | Construction | 2007 |
| Dawes Sewing Limited | Wholesale & retail | 2012 |
| Dawkes Music & Windcraft Limited | Wholesale & retail | 1992 |
| Dawntek Distribution Ltd. | Wholesale & retail | 2012 |
| Dawson's Auctioneers Limited | Other services | 2016 |
| DB Fire and Risk Ltd | Financial services | 2025 |