| ALL for Cars Ltd | Wholesale & retail | 2019 |
| ALL in One Distributors Limited | Other services | 2021 |
| ALL Seasons Air Conditioning and Heating Solutions Ltd | Energy | 2019 |
| ALL Simple Internet Services LLP | | 2010 |
| ALL Things Made New Limited | Construction | 2011 |
| ALL Things Small Limited | Wholesale & retail | 2023 |
| Allaero Limited | Transport & logistics | 1988 |
| Alldis Electrical Ltd | Construction | 2025 |
| Allington Dental Care Ltd | Health & social care | 2010 |
| Allstore Systems Limited | Construction | 2004 |
| Allstore Systems South Limited | Construction | 2023 |
| Almd Holdings Ltd | Financial services | 2026 |
| Almeida Resources Limited | Administrative & support | 2025 |
| Almost Media Limited | Information & communication | 2026 |
| Aloha Paradise Ltd | Professional & scientific | 2014 |
| Alora & Alora Ltd | Manufacturing | 2022 |
| Alora’S Beauty Ltd | Other services | 2025 |
| Alpha 17 Training Ltd | Education | 2025 |
| Alpha Aliment Ltd | Professional & scientific | 2013 |
| Alpha Aviation Parts Limited | Transport & logistics | 2018 |
| Alpha Cars Crawley Ltd | Transport & logistics | 2018 |
| Alpha FIX Limited | Construction | 2024 |
| Alpha Maintenance & Clearance Limited | Water & waste | 2015 |
| Alpha Mortgage Services Limited | Financial services | 2020 |
| Alpha Scaffolding Limited | Construction | 2011 |
| Alpha Services Group Ltd | Water & waste | 2026 |
| Alpha Star Healthcare Limited | Health & social care | 2019 |
| Alpha Vision Healthcare Ltd | Health & social care | 2022 |
| ALPHA25 Ltd | Professional & scientific | 2023 |
| Alphaquarry Global Markets Ltd | Financial services | 2018 |
| Alpi Barber Ltd | Health & social care | 2012 |
| Alpiine Traders Ltd | Manufacturing | 2026 |
| Alpine Traders Limited | Wholesale & retail | 2020 |
| ALS Fire Protection Limited | Construction | 2016 |
| Altechnologies Ltd | Manufacturing | 2019 |
| Alterra Solutions Limited | Information & communication | 2016 |
| Altu Services Limited | Information & communication | 2026 |
| Alveez Limited | Wholesale & retail | 2025 |
| Alvi Motors Ltd | Wholesale & retail | 2025 |
| Always Heating and Plumbing Ltd | Construction | 2022 |
| Alōr Skin Science Ltd | Wholesale & retail | 2024 |
| AM Finflow UK Ltd | Manufacturing | 2018 |
| AM Happy Days Ltd | Administrative & support | 2017 |
| AM Real Consultancy Ltd | Professional & scientific | 2014 |
| AMA Property Management Ltd | Real estate | 2024 |
| AMA Security and Fire Ltd | Professional & scientific | 2022 |
| Amaani Security Limited | Administrative & support | 2025 |
| Amadeus Health and Medical Ltd | Administrative & support | 2021 |
| Amadou Kamara Ltd | Health & social care | 2019 |
| Amahlia Logistics Ltd | Wholesale & retail | 2026 |
| Amalya Skincare Ltd | Other services | 2022 |
| Amanda Mccarthy Life Coaching Limited | Health & social care | 2021 |
| Amanii Services Ltd | Wholesale & retail | 2022 |
| Amant MEA Building & Home Improvement Services Ltd | Construction | 2020 |
| Amara Laser and Beauty Clinic Limited | Other services | 2015 |
| Amaral Capital Ltd | Professional & scientific | 2022 |
| Amaya Hope Limited | Health & social care | 2022 |
| Amazone OUT Ltd | Wholesale & retail | 2024 |
| AMB Consultancy Services Ltd | Professional & scientific | 2018 |
| AMB Metal Recycling Limited | Water & waste | 2020 |
| Ambassador Chie Masiziba Limited | Manufacturing | 2024 |
| Ambassadors Choice Limited | Wholesale & retail | 1987 |
| Amber Emerald Limited | Real estate | 2024 |
| Amber Transport Ltd | Transport & logistics | 2023 |
| Ambermeds Solutions Ltd | Health & social care | 2023 |
| AMD Automation Ltd | Professional & scientific | 2018 |
| AMD Dlugosz Ltd | Administrative & support | 2019 |
| AMD Services and Solutions Ltd | Transport & logistics | 2017 |
| Amelia DC Ltd | Wholesale & retail | 2024 |
| Amethyst Retailing (UK) Ltd | Wholesale & retail | 2024 |
| Amfr Properties Ltd | Real estate | 2021 |
| Amica Accounting Limited | Professional & scientific | 2018 |
| Amica Construction UK Limited | Construction | 2015 |
| Amini Corp UK Limited | Information & communication | 2023 |
| Aminrup Investment Management Ltd | Real estate | 2016 |
| Amira Projects Limited | Construction | 2017 |
| Amma Consulting Ltd | Other services | 2025 |
| Amma Ventures Ltd | Hospitality | 2019 |
| Amman Retails Ltd | Wholesale & retail | 2022 |
| Ammara Kiran Enterprises Ltd | Wholesale & retail | 2025 |
| Ammeyy Limited | Wholesale & retail | 2024 |
| Amoyo Ltd | Health & social care | 2011 |
| AMP Hgroup Ltd | Professional & scientific | 2026 |
| AMR Universal Limited | Wholesale & retail | 2023 |
| Amrail Ltd | Construction | 2023 |
| AMS Robotics (South) Ltd | Manufacturing | 2025 |
| Amster Care Company Ltd | Public administration | 2024 |
| Amstrad Computers Ltd | Wholesale & retail | 2026 |
| AMV Development Group Ltd | Construction | 2026 |
| AMY Studio Ltd | Wholesale & retail | 2024 |
| ANA & Co. Ltd | Wholesale & retail | 2014 |
| Ananassa Consulting Ltd | Professional & scientific | 2024 |
| Ananda Nilayam Ltd | Real estate | 2025 |
| Ananth & JS Investments Ltd | Real estate | 2020 |
| Ananth & JS Ltd | Information & communication | 2013 |
| Anda Products Limited | Manufacturing | 1920 |
| Andesite Homes Ltd | Real estate | 2023 |
| Andre's Haulage Ltd | Transport & logistics | 2019 |
| Andrei Promotions Ltd | Other services | 2015 |
| Andremar Services Ltd | Transport & logistics | 2021 |