| ACTIVE4LUTON Limited | Arts & recreation | 2013 |
| Actsure Systems Limited | Construction | 1991 |
| Actualised Ltd | Professional & scientific | 2021 |
| Acumen Accountants Ltd | Professional & scientific | 2024 |
| Acumen Accounting Oxford Limited | Professional & scientific | 2017 |
| Acura Engineering Consultants Ltd | Professional & scientific | 2021 |
| AD Builders (Luton) Ltd | Construction | 2023 |
| AD Capital Consultant Ltd | Professional & scientific | 2024 |
| AD Design and Print Limited | Information & communication | 2019 |
| AD Motor Group Ltd | Wholesale & retail | 2025 |
| Ad.Bunny Ltd | Professional & scientific | 2025 |
| ADA Express Trans Ltd | Transport & logistics | 2016 |
| Adam Car Keys Ltd | Other services | 2025 |
| Adam Consultancy PVT Ltd | Professional & scientific | 2025 |
| Adam Motorcycles Ltd | Wholesale & retail | 2023 |
| Adam Wells & Co Ltd | Households | 2021 |
| Adams Strategic Consultancy Ltd | Information & communication | 2026 |
| ADAMVDV6 Limited | Wholesale & retail | 2015 |
| Adan Traders Ltd | Wholesale & retail | 2025 |
| Adarash Plumbing Ltd | Construction | 2019 |
| Adas Auto Electrical GEO Services Ltd | Manufacturing | 2012 |
| Adassa Productions Limited | Information & communication | 2013 |
| ADB Sierra Ltd | Construction | 2018 |
| ADB W&G Services Limited | Extraterritorial | 2021 |
| Addiom Ltd | Wholesale & retail | 2016 |
| Addware Industries Limited | Manufacturing | 2026 |
| Ade-K Ventures Ltd | Professional & scientific | 2019 |
| Aded Ltd | Transport & logistics | 2024 |
| Adekofo Ltd | Energy | 2016 |
| Adekop Ltd | Transport & logistics | 2018 |
| Adela & Sarah Ltd | Construction | 2023 |
| Adela Pantiru Ltd | Administrative & support | 2026 |
| Adelaide Jase Consulting Ltd | Extraterritorial | 2021 |
| Adelaidejase Developments Ltd | Real estate | 2022 |
| Adelmed Limited | Health & social care | 2021 |
| Adelphia Limited | Information & communication | 2012 |
| Aden Auto Ltd | Wholesale & retail | 2020 |
| Aden Residence Ltd | Real estate | 2025 |
| Adept Plumbing & Heating Solutions Ltd | Construction | 2019 |
| ADEX360 Ltd | Professional & scientific | 2024 |
| Adeye Logistic Limited | Transport & logistics | 2019 |
| ADI Property Management Ltd | Households | 2024 |
| Adiel Legal Limited | Professional & scientific | 2024 |
| Adikted Burger Ltd | Hospitality | 2023 |
| Adil&Nauman Limited | Professional & scientific | 2014 |
| Adilbins&Co Limited | Wholesale & retail | 2026 |
| Adiray Construct Ltd | Construction | 2025 |
| ADJ Electrical & Maintenance Ltd | Construction | 2023 |
| Adja Limited | Transport & logistics | 2025 |
| Adlington Court Management Limited | Households | 1969 |
| Admiral Express Ltd | Transport & logistics | 2022 |
| Admiral Horatio Nelson Ltd | Construction | 2020 |
| ADN Traders Limited | Wholesale & retail | 2025 |
| Adnerb Limited | Health & social care | 2023 |
| Adnexus Global Limited | Wholesale & retail | 2025 |
| Adobe Productions Limited | Information & communication | 2024 |
| Adobe Properties Limited | Construction | 2020 |
| Adomnita Construction Limited | Construction | 2022 |
| Adon Construction Ltd | Construction | 2019 |
| Ador Holding Ltd | Wholesale & retail | 2026 |
| Adorate Ltd | Wholesale & retail | 2020 |
| Adorn by Lorr Ltd | Other services | 2026 |
| ADR Luton Ltd | Transport & logistics | 2026 |
| Adrian Haughton Ltd | Transport & logistics | 2025 |
| Adrian MED Services Ltd | Health & social care | 2024 |
| Adrian Varol Ltd | Construction | 2026 |
| Adrian's Joinery Ltd | Construction | 2015 |
| Adriana Electronics Ltd | Wholesale & retail | 2020 |
| Adriatyka Ltd | Hospitality | 2024 |
| Adroit Business Consultancy Limited | Professional & scientific | 2020 |
| Adroit Precision Engineering Limited | Manufacturing | 1998 |
| Adroit Sports Management (ASM) Ltd | Arts & recreation | 2019 |
| Adroitive Ltd | Information & communication | 2017 |
| Adryan Construct Limited | Construction | 2026 |
| Adsmart TV Ltd | Professional & scientific | 2017 |
| Adspec Media Ltd | Professional & scientific | 2019 |
| Adtm Ltd | Transport & logistics | 2019 |
| ADV Contractors Limited | Construction | 2025 |
| ADV. Martin Express Logistics Limited | Transport & logistics | 2025 |
| Advance DRY Clean Ltd | Other services | 2008 |
| Advance Electric Services Ltd | Manufacturing | 2011 |
| Advance ISW Ltd | Health & social care | 2017 |
| Advance Leap International Limited | Information & communication | 2025 |
| Advance Point Solutions Limited | Information & communication | 2025 |
| Advanced Adult Care Services Ltd | Health & social care | 2015 |
| Advanced Dynamics London Limited | Construction | 2017 |
| Advanced Enterprise Solutions Ltd | Real estate | 2025 |
| Advanced Payment Ecosystems Limited | Information & communication | 2022 |
| Advanced Refinish Solutions Limited | Manufacturing | 2025 |
| Advanced Witness Systems Limited | Manufacturing | 1990 |
| Advanceonline Ltd | Transport & logistics | 2020 |
| Advantage Church Ltd | Other services | 2026 |
| Advise and Olas Limited | Professional & scientific | 2019 |
| Advistas Associates Ltd | Extraterritorial | 2012 |
| ADW Financial Management Limited | Professional & scientific | 2012 |
| Adway Ltd | Professional & scientific | 2020 |
| Adysson Construction Ltd | Construction | 2019 |
| Adzware Ltd | Wholesale & retail | 2024 |
| AE Commerce Group Ltd | Wholesale & retail | 2026 |
| AE Repairs Ltd | Wholesale & retail | 2025 |