| Acube Digital Limited | Information & communication | 2024 |
| Acueva Accountancy and Tax Services Ltd. | Professional & scientific | 2024 |
| Acumed Data Ltd | Professional & scientific | 2010 |
| Acumen 11 Limited | Real estate | 2020 |
| Acumen Homes Ltd | Real estate | 2016 |
| Acumen House Holdings Limited | Other services | 2017 |
| Acupeople Ltd | Professional & scientific | 2022 |
| Acuteagility Ltd | Information & communication | 2023 |
| AD & SB Ltd | Hospitality | 2021 |
| AD Salon Limited | Other services | 2005 |
| AD Surgical Care Limited | Health & social care | 2021 |
| AD Technologies Limited | Professional & scientific | 2006 |
| Ad-Moto Limited | Information & communication | 2020 |
| Adabra Ltd | Wholesale & retail | 2025 |
| Adam Kelly Consulting Limited | Information & communication | 2018 |
| Adam PAY Associates Limited | Professional & scientific | 1992 |
| Adam Wallinger Limited | Manufacturing | 2013 |
| Adam's Plumbing Service Limited | Construction | 2024 |
| Adama Agricultural Solutions UK Ltd | Manufacturing | 1988 |
| Adamant Properties Ltd | Real estate | 2022 |
| Adamo Marketing Solutions Limited | Professional & scientific | 2025 |
| Adams Bespoke Joinery London Ltd | Manufacturing | 2024 |
| Adams EST Investments Ltd | Real estate | 2021 |
| Adams Estates Ltd | Real estate | 2004 |
| Adams Kebab Ltd | Hospitality | 2025 |
| Adams Logistic Solutions Limited | Transport & logistics | 2026 |
| Adams Motors Reading Limited | Wholesale & retail | 2020 |
| Adapted Vehicle Hire Limited | Administrative & support | 2005 |
| Adaptick Group Ltd | Information & communication | 2025 |
| Adaptick Limited | Information & communication | 2024 |
| Adaptisys Info Solutions Limited | Information & communication | 2018 |
| Adar Property Reading Limited | Real estate | 2021 |
| Adarji Consulting Limited | Information & communication | 2026 |
| Adarsh Arun Private Limited | Information & communication | 2009 |
| Adastra 21 Ltd | Information & communication | 2025 |
| Adastra Group Holdings Limited | Information & communication | 2016 |
| Adattivo Limited | Professional & scientific | 2014 |
| ADB8 Ventures Limited | Information & communication | 2023 |
| ADC Building Solutions Ltd | Construction | 2018 |
| ADC Therapeutics (UK) Limited | Professional & scientific | 2014 |
| Adcamp LLP | | 2008 |
| Adcastle Limited | Real estate | 2019 |
| ADD One Limited | Information & communication | 2012 |
| ADD Style UK Limited | Other services | 2008 |
| Addict London Limited | Information & communication | 2018 |
| Addidi Angels 2 LLP | | 2011 |
| Addidi Angels LLP | | 2008 |
| Addidi Holdings Nominee Limited | Administrative & support | 2018 |
| Addington Consulting Ltd | Information & communication | 2018 |
| Addington House Residents Association Ltd | Households | 1987 |
| Addison Gardens Management Company Newbury Ltd | Administrative & support | 2018 |
| Address Enterprise Limited | Health & social care | 2020 |
| Addsecure Limited | Information & communication | 1998 |
| Addy Estate Limited | Real estate | 2025 |
| Adeco Excel LLP | | 2010 |
| Adelantum Limited | Professional & scientific | 2021 |
| Adelus Consulting Limited | Professional & scientific | 2011 |
| Adelzek Limited | Health & social care | 2025 |
| Adenyo Otieno Ltd | Other services | 2021 |
| Adept Heating & Plumbing Limited | Construction | 2010 |
| Adesuwa Ltd | Health & social care | 2021 |
| Adetcon Ltd | Information & communication | 2019 |
| Adex International Limited | Real estate | 2010 |
| Adexe Limited | Information & communication | 2016 |
| Adeyu Catering Limited | Hospitality | 2025 |
| ADF Technology Solutions Ltd | Professional & scientific | 2020 |
| ADG Commercial & Domestic Ltd | Construction | 2023 |
| ADH Lettings Ltd | Real estate | 2022 |
| Adhisha Investments Ltd | Real estate | 2023 |
| Adhisha Technologies Ltd | Information & communication | 2019 |
| Adhita Limited | Wholesale & retail | 2022 |
| ADI Consultants Limited | Professional & scientific | 2013 |
| Adina Monette Ltd. | Wholesale & retail | 2016 |
| Adish Ltd | Real estate | 2024 |
| Adlam Consultants Limited | Transport & logistics | 2021 |
| Adler Manufacturing Limited | Administrative & support | 1989 |
| Adler SPV Holdings Ltd | Real estate | 2024 |
| ADM Plumbing & Heating Services Ltd | Construction | 2021 |
| Admg Properties Limited | Construction | 2004 |
| Adminshield Limited | Information & communication | 2026 |
| Admiralty Finance Ltd | Professional & scientific | 2019 |
| Admire Your Floor Ltd. | Other services | 2006 |
| Adnan Car Hire Ltd | Administrative & support | 2023 |
| Adnil Limited | Information & communication | 2012 |
| Adonia Architectural Ltd | Professional & scientific | 2015 |
| Adoptarx Ltd | Professional & scientific | 2025 |
| Adorn Decorating Ltd | Construction | 2022 |
| Adot Delivery’S Ltd | Transport & logistics | 2020 |
| Adrian Paul Creations Limited | Construction | 2015 |
| ADS Actuarial Limited | Administrative & support | 2015 |
| ADS NO. 3 Ltd | Professional & scientific | 2021 |
| Adsa Residential Limited | Administrative & support | 2006 |
| ADT Build Ltd | Real estate | 2019 |
| ADT Support Ltd | Administrative & support | 2019 |
| Adum Limited | Hospitality | 2018 |
| Adut Limited | Hospitality | 2018 |
| Advaice Limited | Information & communication | 2025 |
| Advaita Pharmaceutical and Clinical Services Limited | Information & communication | 2015 |
| Advance Glass Doors & Windows Ltd | Manufacturing | 2014 |
| Advance Gym Ltd | Arts & recreation | 2019 |