| Alex White Golf Limited | Wholesale & retail | 2011 |
| Alexander Plumbing and Heating (Beds) Limited | Construction | 2021 |
| Alexandra Court Management Company (Linslade) Limited | Households | 2001 |
| Alexandra Park (High Wycombe) Residents (Two) Limited | Households | 1993 |
| Alexandra Park (High Wycombe) Residents Limited | Real estate | 1992 |
| Alexia Loves Limited | Wholesale & retail | 2025 |
| Alfa Intelligence Limited | Information & communication | 2023 |
| Algorhythm Labs Limited | Information & communication | 2025 |
| Ali-Lala Limited | Information & communication | 2014 |
| Alication Ltd | Hospitality | 2022 |
| Alice Healthcare Ltd | Health & social care | 2025 |
| Alice Ingle Designs Ltd | Professional & scientific | 2022 |
| Alice Skewis Jewellery Ltd | Wholesale & retail | 2023 |
| Alikat Property Ltd | Administrative & support | 2020 |
| Alison Healthcare Ltd | Health & social care | 2024 |
| ALL About Drainage Limited | Construction | 2021 |
| ALL About ME Fitness Ltd | Arts & recreation | 2015 |
| ALL Access Solutions Ltd | Construction | 2009 |
| ALL Builds Construction Limited | Construction | 2025 |
| ALL Cars & Services Limited | Wholesale & retail | 2021 |
| ALL Seasons DRY Cleaners Ltd | Other services | 2018 |
| ALL Travel Solutions Ltd | Administrative & support | 2021 |
| ALL Type Roofing and Guttering Ltd | Construction | 2025 |
| Allaperto Limited | Wholesale & retail | 2021 |
| Allen's E-Bikes Ltd | Wholesale & retail | 2020 |
| Allens Building Services Limited | Construction | 2009 |
| Alliance Associates Limited | Professional & scientific | 2008 |
| Alliance Systems Ltd | Information & communication | 1996 |
| Allidata Limited | Information & communication | 2022 |
| Allsmarts Advisory Limited | Information & communication | 2022 |
| Alltech Signs and Graphics Limited | Manufacturing | 2005 |
| Alpha Court RTM Company Limited | Households | 2024 |
| Alphaclub Business Solutions Ltd | Information & communication | 2011 |
| ALR Healthcare Limited | Education | 2023 |
| Alsford Wharf Estate Limited | Real estate | 1997 |
| Alsford Wharf RTM Company Limited | Real estate | 2005 |
| Alston Trading Group Limited | Professional & scientific | 2022 |
| Altair IV Consulting Limited | Information & communication | 2026 |
| Altemeyer Business Analytics Limited | Professional & scientific | 2020 |
| Alto Living Limited | Professional & scientific | 2020 |
| Altra IT Limited | Information & communication | 2010 |
| Alupului Ltd | Construction | 2015 |
| Alura Group UK Ltd | Professional & scientific | 2020 |
| Alvaros Supply Chain Limited | Professional & scientific | 2019 |
| AM 2 PM Property Group Ltd | Real estate | 2026 |
| AM 2 PM Scaffolding Ltd | Construction | 2019 |
| AM Support Ltd | Education | 2024 |
| Amadasun Heathcare Limited | Health & social care | 2019 |
| Amalgamated Builders (Holdings) Limited | Professional & scientific | 1984 |
| Amalgamated Properties (Tring) Limited | Real estate | 1964 |
| Amalgamated Skips Limited | Water & waste | 2012 |
| Amaric Associates Limited | Wholesale & retail | 2013 |
| AMB Services Ltd | Extraterritorial | 1997 |
| Amber Mechanical Services Limited | Construction | 2014 |
| Amber-Jane Dance Ltd | Arts & recreation | 2025 |
| Amcy Ltd | Wholesale & retail | 2026 |
| AME Candle Studio Ltd | Wholesale & retail | 2020 |
| Ameenmedia Limited | Information & communication | 2007 |
| Ameerah Healthcare Ltd | Health & social care | 2025 |
| Amica Consultancy Ltd | Professional & scientific | 2026 |
| AMJ Optical Ltd | Health & social care | 2021 |
| AMN Services Ltd | Construction | 2025 |
| Amora Capital Ltd | Hospitality | 2025 |
| Amore Marketing Ltd | Information & communication | 2019 |
| Amortech Limited | Information & communication | 2006 |
| Amour Music Limited | Arts & recreation | 2013 |
| Amp'D UP Electrical Ltd | Construction | 2016 |
| Amped UP Electrical Ltd | Construction | 2020 |
| AMR Auto Services Limited | Wholesale & retail | 2004 |
| Amvek Healthcare Ltd | Health & social care | 2025 |
| AMY C Healthcare & Medico-Legal Ltd | Health & social care | 2025 |
| AN Recycling Limited | Wholesale & retail | 2026 |
| ANA Ka'Ike Limited | Professional & scientific | 2017 |
| Anaka Partners Limited | Professional & scientific | 2023 |
| Anchor 23 Ltd | Real estate | 2024 |
| Anchor Electrical Ltd | Construction | 2018 |
| Anderson Clinical Search Limited | Administrative & support | 2025 |
| Anderton Electrics Limited | Construction | 2013 |
| Anderton Lettings Ltd | Real estate | 2024 |
| Andhere Group Ltd | Hospitality | 2025 |
| Andrea Pitrik Garden Design Ltd | Professional & scientific | 2024 |
| Andrew Whitehouse Associates Limited | Financial services | 2012 |
| Andrews Residential Limited | Real estate | 2020 |
| Andy & Sparking Ltd | Administrative & support | 2018 |
| Angel Promotions Management Limited | Arts & recreation | 2018 |
| Angle Care Ltd | Health & social care | 2018 |
| Anglia Property Management Limited | Households | 2007 |
| Anglian Rover Owners' Club Limited | Arts & recreation | 1980 |
| Ania Ruszkowski Training Ltd | Professional & scientific | 2020 |
| Aniko's Dance Academy Ltd | Arts & recreation | 2016 |
| Aniseed PR Limited | Professional & scientific | 2009 |
| Anjali Consulting Limited | Information & communication | 2010 |
| Anna Raverat Consultancy Limited | Professional & scientific | 2018 |
| Another FOX Ltd | Wholesale & retail | 2017 |
| Another One Ltd | Wholesale & retail | 2023 |
| Ansah Consulting Limited | Information & communication | 2024 |
| Anticuus Partners Ltd | Administrative & support | 2015 |
| Antlyon Consulting Limited | Information & communication | 2022 |
| Antsnest Games Ltd | Manufacturing | 2025 |
| Anugbule & Sons Ltd | Health & social care | 2022 |