| D & C Labour Suppliers Limited | Professional & scientific | 1999 |
| D & G Properties (Central) Limited | Hospitality | 2024 |
| D & S Swans Limited | Real estate | 2019 |
| D a Coley Limited | Wholesale & retail | 2020 |
| D and E Plant Hire Limited | Administrative & support | 2024 |
| D G Sports Consultancy Limited | Education | 2014 |
| D G W Management Services Limited | Information & communication | 2015 |
| D H Auto Services (Luton) Limited | Wholesale & retail | 2010 |
| D Harmer Developments Limited | Construction | 2018 |
| D Harrington Communications Limited | Professional & scientific | 2015 |
| D Nesbit Consulting Ltd | Professional & scientific | 2021 |
| D P Newton Limited | Water & waste | 2021 |
| D Parke Haulage Ltd | Transport & logistics | 2007 |
| D&A Davies Limited | Administrative & support | 2015 |
| D&D Auto Refine Ltd | Wholesale & retail | 2025 |
| D&D Linguistics Limited | Professional & scientific | 2025 |
| D&G Lettings (Central) Limited | Real estate | 2026 |
| D&K Property Ltd | Real estate | 2026 |
| D&S Building Services Ltd | Construction | 2026 |
| D-Carbon Alliance Ltd | Professional & scientific | 2025 |
| D. Connold & Company Limited | Real estate | 1979 |
| D. Elliott and Sons Limited | Construction | 2005 |
| D. J. & M. Plumbing Services Limited | Construction | 2003 |
| D.K Plumbing and Maintenance Ltd | Other services | 2022 |
| D.O.C Security Ltd | Administrative & support | 2022 |
| D.T.S Management Limited | Professional & scientific | 2008 |
| D15 Holdings Ltd | Real estate | 2020 |
| D15 Real Estate Limited | Real estate | 2020 |
| D2 Artworks Limited | Arts & recreation | 2014 |
| D2 Management Limited | Real estate | 2023 |
| D2D Removals Ltd | Transport & logistics | 2025 |
| DA Vinci Traders Ltd | Wholesale & retail | 2015 |
| DAC Scenery Limited | Construction | 2025 |
| Dagnall Management Company (ST. Albans) Limited | Households | 1990 |
| Dahlia Health Care Services Ltd | Health & social care | 2013 |
| Daigo Ltd | Wholesale & retail | 2020 |
| Daktari Partnership Ltd | Manufacturing | 2011 |
| Dalemore Limited | Information & communication | 2022 |
| Dallaglio 8 LLP | | 2007 |
| Daluc Limited | Professional & scientific | 2019 |
| Daly Consultancy Limited | Professional & scientific | 2015 |
| DAN James Construction Ltd | Construction | 2011 |
| DAN Synge Ltd | Construction | 2015 |
| Danebury Associates Limited | Administrative & support | 2023 |
| Dani Building Contractors Limited | Construction | 2018 |
| Daniel Coburn Limited | Financial services | 2011 |
| Daniel George Levy Limited | Real estate | 2023 |
| Daniel Minall Limited | Professional & scientific | 2008 |
| Danielle Autos Limited | Wholesale & retail | 2023 |
| Danielle Commercial Limited | Real estate | 2026 |
| Danielle UK Limited | Real estate | 2007 |
| Danietech Ltd | Construction | 2014 |
| Danimon Limited | Administrative & support | 2017 |
| Danmax Transport Limited | Transport & logistics | 2009 |
| Dansar Lettings Limited | Real estate | 2013 |
| Dansar Properties Limited | Real estate | 1998 |
| Dansen Properties Limited | Real estate | 2025 |
| DARA5 Nominees Ltd | Financial services | 2022 |
| Darcy Creative Ltd | Professional & scientific | 2026 |
| Dark Horse Marketing Limited | Professional & scientific | 2021 |
| Dark Matrix Ltd | Professional & scientific | 2018 |
| Dark Sand Ltd | Wholesale & retail | 2019 |
| Darock Projects International Limited | Wholesale & retail | 2022 |
| Darock Projects Limited | Information & communication | 2008 |
| Darock Properties Limited | Real estate | 2024 |
| Darrom Ltd | Other services | 2015 |
| Data Horse Capital LLP | | 2022 |
| Data Network Integration Services Limited | Manufacturing | 1998 |
| Data Support (UK) Ltd | Information & communication | 2022 |
| Data-Cuff Ltd | Professional & scientific | 2016 |
| Dataly Ltd | Professional & scientific | 2022 |
| Datalytix Consulting Limited | Information & communication | 2023 |
| Datasect Limited | Extraterritorial | 2024 |
| Dataseven IT Services Limited | Information & communication | 2022 |
| Datasharp Independent Solutions Limited | Administrative & support | 2003 |
| Davanti Recruitment Limited | Administrative & support | 2009 |
| Dave PAY Group Ltd | Construction | 2025 |
| David Chadwick Ltd | Real estate | 2020 |
| David Peter (Holdings) Ltd | Wholesale & retail | 2022 |
| David Peter (Retail) Ltd. Ltd | Wholesale & retail | 2026 |
| David Simon Associates Limited | Professional & scientific | 2007 |
| David Stead Financial Services Ltd | Professional & scientific | 2014 |
| Davidson Deem Limited | Financial services | 2001 |
| Davis Bespoke Homes Ltd | Construction | 2025 |
| Davis Group Holdings Limited | Financial services | 2021 |
| Davis Property Group Holdings Ltd | Financial services | 2026 |
| Dawn Real Estate Investments Ltd | Real estate | 2020 |
| Day Brothers Colney Heath LLP | | 2014 |
| Daybreak Creative Limited | Arts & recreation | 2008 |
| Days Autospa Ltd | Other services | 2025 |
| DB Building Services Ltd | Construction | 2021 |
| DB Dairies Limited | Wholesale & retail | 2006 |
| DB Renovations Design and Build Ltd | Construction | 2017 |
| DBB Enterprises Ltd | Arts & recreation | 2026 |
| Dbiggs Associates Ltd | Professional & scientific | 2020 |
| DBO PAY Ltd | Administrative & support | 2025 |
| Dboi Delight Enterprise Ltd | Health & social care | 2022 |
| DBS Holdings and Investments Ltd | Financial services | 2025 |
| DBW Health Consulting Limited | Health & social care | 2023 |
| DC Fire Expert Limited | Administrative & support | 2019 |