| A R Signalling Solutions Limited | Construction | 2013 |
| A Route Ltd | Transport & logistics | 2026 |
| A S D Accountancy Services Ltd | Professional & scientific | 2003 |
| A S Gardens & Ground Maintenance Limited | Administrative & support | 2010 |
| A S R Chowdhury Limited | Hospitality | 2023 |
| A S S E T Technologies Ltd | Manufacturing | 2019 |
| A Secret Garden Ltd | Hospitality | 2025 |
| A Singh Private Limited | Professional & scientific | 2025 |
| A Space: Growing Creative Communities Ltd | Arts & recreation | 2009 |
| A Star Reno Ltd | Construction | 2024 |
| A T Professional Facilities Services Ltd | Administrative & support | 2023 |
| A Taxi Ltd | Transport & logistics | 2023 |
| A to B Removals Direct Ltd | Transport & logistics | 2025 |
| A to B Transportation Ltd | Water & waste | 2025 |
| A to B Waste Management Ltd | Water & waste | 2024 |
| A to Z Building and Groundworks Limited | Construction | 2018 |
| A to Z Electrical Solutions Ltd | Manufacturing | 2022 |
| A Town Carpentry Ltd | Manufacturing | 2025 |
| A Twist of Lime Limited | Professional & scientific | 2019 |
| A V Electrical (Southern) Ltd | Construction | 2006 |
| A W Carpentry & Loft Conversions Ltd | Manufacturing | 2012 |
| A W Surveying Limited | Professional & scientific | 2013 |
| A Watts Marine Electrical Limited | Manufacturing | 2025 |
| A YL Wong Ltd | Wholesale & retail | 2023 |
| A&B Best Trans Ltd | Transport & logistics | 2019 |
| A&B Conditioned Air Limited | Construction | 2018 |
| A&B Photo Design Limited | Wholesale & retail | 2025 |
| A&B Supermarkets Ltd | Wholesale & retail | 2025 |
| A&F Garage Ltd | Wholesale & retail | 2025 |
| A&G Maintenance Services Ltd | Other services | 2025 |
| A&G Phillips Consultancy Limited | Health & social care | 2016 |
| A&G Shirley Ltd | Water & waste | 2014 |
| A&G Valeanu Ltd | Construction | 2017 |
| A&L Stays Limited | Households | 2026 |
| A&M Aylesbury Limited | Real estate | 2022 |
| A&M Consulting (SE) Limited | Professional & scientific | 2014 |
| A&M for Ever Delivery Ltd | Transport & logistics | 2025 |
| A&M Mandair Limited | Professional & scientific | 2022 |
| A&M Trans Ltd | Transport & logistics | 2016 |
| A&M Transfer Limited | Transport & logistics | 2022 |
| A&N Electrical Services Ltd | Construction | 2024 |
| A&N Store Ltd | Wholesale & retail | 2020 |
| A&O Bookkeeping Services Ltd | Professional & scientific | 2025 |
| A&P Painting Contractors Limited | Construction | 2022 |
| A&P Sewing Ltd | Wholesale & retail | 2022 |
| A&R Automobiles Ltd | Wholesale & retail | 2019 |
| A&Rs Solutions Ltd | Hospitality | 2021 |
| A&S B Properties Limited | Real estate | 2017 |
| A&S Building Services South Ltd | Construction | 2019 |
| A&S Courier Services Ltd | Transport & logistics | 2022 |
| A&T Instruments Ltd | Wholesale & retail | 2015 |
| A&T Ponds and Pools Ltd | Construction | 2015 |
| A&Z Japan Hybrid Cars Ltd | Wholesale & retail | 2026 |
| A&Z Soton Limited | Hospitality | 2025 |
| A-Cute Medical Event Services Limited | Health & social care | 2013 |
| A-Tel Solutions Limited | Information & communication | 2012 |
| A-Z Cleaning Service Ltd | Administrative & support | 2024 |
| A-Z Property Relocation Global Limited | Real estate | 2021 |
| A. D. (Southern) Limited | Construction | 2010 |
| A. J. Bull Scaffolding Limited | Construction | 1999 |
| A. Medway Limited | Construction | 1999 |
| A. P. Smith Roofing Limited | Construction | 2018 |
| A. Withey Paving Limited | Construction | 2013 |
| A.A General Services Ltd | Other services | 2023 |
| A.B. Medical Services Limited | Health & social care | 2003 |
| A.B. Plant Shipping Ltd | Transport & logistics | 1987 |
| A.B.L Trading Ltd | Wholesale & retail | 2024 |
| A.B.P. Associates Limited | Professional & scientific | 2000 |
| A.C.G. Contractors Limited | Construction | 2014 |
| A.C.L. Plastering and Drylining Limited | Construction | 1991 |
| A.C.M.E Homes (Properties) Limited | Real estate | 2019 |
| A.D.S. Properties North East Ltd | Households | 2025 |
| A.E. Worley & SON Limited | Wholesale & retail | 1965 |
| A.E.Roberts(Fruitgrower & Nurseryman)Limited | Agriculture & fishing | 1950 |
| A.H. Livestock Services Limited | Agriculture & fishing | 2013 |
| A.H. Sultan Ltd | Extraterritorial | 2024 |
| A.I.M Capital Group Limited | Financial services | 2026 |
| A.J Technologies Limited | Information & communication | 2025 |
| A.J.P Solutions Ltd | Construction | 2014 |
| A.K. Willcox Limited | Professional & scientific | 1984 |
| A.M. Mechanical Limited | Wholesale & retail | 2015 |
| A.P Dance Collaborations Ltd | Education | 2024 |
| A.R. Vehicle Solutions Ltd | Wholesale & retail | 2019 |
| A.R.T Scaffolding Services Ltd | Construction | 2025 |
| A.S Industries Ltd | Water & waste | 2021 |
| A.S. Taxis Limited | Transport & logistics | 2002 |
| A.T Nails Spa Southampton Ltd | Other services | 2023 |
| A.U.H. Transport Services Ltd | Transport & logistics | 2025 |
| A.W. Freeman Limited | Extraterritorial | 1957 |
| A1 Car New Forest Ltd | Other services | 2013 |
| A1 Car Wash Ltd | Administrative & support | 2025 |
| A1 Carpet Cleaning & Upholstery South East Ltd | Other services | 2019 |
| A1 Carpet Cleaning Chichester Ltd | Other services | 2022 |
| A1 Carpets Southern Ltd | Construction | 2009 |
| A1 Complete Plumbing & Heating Ltd | Construction | 2007 |
| A1 Driving School Ltd | Education | 2024 |
| A1 Marine Electronics Limited | Manufacturing | 2020 |
| A1 Places Ltd | Real estate | 2025 |
| A1 Powder Coatings (Southampton) Ltd | Manufacturing | 2025 |
| A1 Teaching & Learning Ltd | Education | 2023 |