| Airford Limited | Real estate | 1994 |
| Airscape Solutions Ltd | Construction | 2023 |
| Aiwa Group Ltd | Construction | 2015 |
| AJ Foster Editorial Services Limited | Manufacturing | 2021 |
| AJ Kitchen Ltd | Hospitality | 2025 |
| AJ Plumbing&Building Services Limited | Construction | 2023 |
| AJ Reynolds Consulting Ltd | Professional & scientific | 2020 |
| AJ Safety Specialists Limited | Administrative & support | 2016 |
| AJC International Consultancy Ltd | Professional & scientific | 2012 |
| Ak@Homes Ltd | Hospitality | 2025 |
| Akashco LLP | | 2017 |
| AKE Solutions Ltd | Administrative & support | 2023 |
| Akil Carpentry Ltd | Construction | 2025 |
| Akshayan Limited | Wholesale & retail | 2025 |
| AL Kamil Travel Ltd | Administrative & support | 2025 |
| Alandco Ltd | Manufacturing | 2023 |
| Alannaz Ltd | Hospitality | 2023 |
| Alas Multinational Limited | Health & social care | 2020 |
| Albany Road Freehold Limited | Households | 1993 |
| Albert Butcher Ltd | Wholesale & retail | 2024 |
| Albert Cafe Ltd | Hospitality | 2019 |
| Albert Food Store Ltd | Wholesale & retail | 2025 |
| Albert Lounge Limited | Hospitality | 2026 |
| Albert Meat Limited | Wholesale & retail | 2018 |
| Albert Mini Market Ltd | Wholesale & retail | 2026 |
| Albert Road (Southsea) Management Limited | Households | 2006 |
| Albert Road Laundrycare Limited | Other services | 1996 |
| Albert Road Mini Market Ltd | Wholesale & retail | 2025 |
| Albertspice Ltd | Hospitality | 2024 |
| Albi Car Sales Limited | Wholesale & retail | 2024 |
| Alcourt CIC | Extraterritorial | 2020 |
| ALD Rentals Ltd | Real estate | 2022 |
| Alesol Investment Ltd | Real estate | 2026 |
| Alex Wood Psychology Ltd | Education | 2024 |
| Alexander IV Ltd | Transport & logistics | 2018 |
| ALF Capital Properties Ltd | Real estate | 2025 |
| Algarves Grill I Limited | Hospitality | 2024 |
| Algarves Southsea Ltd | Hospitality | 2026 |
| Alhambra Road Residents Management Limited | Hospitality | 2010 |
| Alice & IVY Limited | Wholesale & retail | 2021 |
| Alison Watson EP Ltd | Education | 2023 |
| ALL Seasons Southern Ltd | Construction | 2013 |
| All-In Sales Development Ltd | Professional & scientific | 2025 |
| Allphase Cleaning Services Ltd | Administrative & support | 2025 |
| Alltypefixing.Av Ltd | Construction | 2014 |
| Alma 2017 Management Company Limited | Real estate | 2017 |
| Alma Valley Healthcare Limited | Administrative & support | 2020 |
| Almamater (UK) Limited | Hospitality | 2001 |
| Alnista Property Ltd | Real estate | 2020 |
| Alpeizak Limited | Professional & scientific | 2025 |
| Alpha Centauri Technologies and Media Solutions Ltd | Information & communication | 2020 |
| Alphen House Portsmouth Management Limited | Households | 1987 |
| Alsaleh Enterprise Limited | Financial services | 2026 |
| Alternative Learning Initiative Group Network CIC | Professional & scientific | 2026 |
| Aluminium Boatbuilding Company Limited | Manufacturing | 2006 |
| Alva Transport Ltd | Transport & logistics | 2023 |
| Always Hair Wigs Limited | Other services | 2026 |
| AM Electrical South Limited | Construction | 2019 |
| AM Property Construction Ltd | Construction | 2024 |
| AM Renewables Limited | Construction | 2025 |
| Amed 23 Limited | Manufacturing | 2026 |
| Amerlynck Engineering Limited | Construction | 2015 |
| Amhp Consultancy Limited | Health & social care | 2012 |
| AMIN98 Ltd | Other services | 2026 |
| Ammari Holdings Ltd | Real estate | 2020 |
| Amworkforce Ltd | Construction | 2016 |
| AMY Melleney Small Animal and Equine Locum Limited | Professional & scientific | 2017 |
| Amzee Media Ltd | Wholesale & retail | 2026 |
| AN Car Sales Ltd | Wholesale & retail | 2023 |
| Analex EDU Ltd | Education | 2022 |
| Anav Fleet Solutions Ltd | Transport & logistics | 2025 |
| AND WE Care Ltd | Administrative & support | 2017 |
| Andali Properties Ltd | Real estate | 2020 |
| Anderson Wind Services Ltd | Manufacturing | 2025 |
| Andprops Limited | Real estate | 1999 |
| Andrew Burns & Sons Ltd | Construction | 2024 |
| Andy Graham Civils Limited | Construction | 2013 |
| Anglo Hispanic Ltd | Other services | 2015 |
| Anglo Marine Overseas Services Limited | Other services | 1998 |
| ANN Barnes Consultancy Limited | Professional & scientific | 2014 |
| Anna's Aesthetics Ltd | Other services | 2025 |
| Anova Data Solutions Ltd | Information & communication | 2018 |
| Anshun Property Ltd | Real estate | 2019 |
| ANT Mechanical Limited | Manufacturing | 2016 |
| Antandtermite Ltd | Professional & scientific | 2026 |
| Anthony Turner Nppf and NIE Training Ltd | Education | 2023 |
| Antonia Salzl Ltd | Health & social care | 2017 |
| Antwon Ltd | Information & communication | 2020 |
| Aobr Limited | Professional & scientific | 2026 |
| AOS Capital Limited | Information & communication | 2014 |
| Apadana Building Management Ltd | Construction | 2025 |
| Aperture Windows & Doors Ltd | Construction | 2023 |
| Apex Bridge Capital Ltd | Construction | 2025 |
| Apex Source Ltd | Wholesale & retail | 2025 |
| Aphesis Limited | Real estate | 1998 |
| APL Engineering Ltd | Construction | 2018 |
| APM Electrical Solutions Ltd | Construction | 2025 |
| Apollo Events UN Ltd | Administrative & support | 2025 |
| Applaud Engineering Ltd | Manufacturing | 2012 |
| Applymove Property Management Limited | Households | 1994 |