| Allegraphy Ltd | Arts & recreation | 2023 |
| Allen Writing Services Limited | Arts & recreation | 2010 |
| Alliance Care (Dales Homes) Limited | Health & social care | 1999 |
| Alliance Global Trading Ltd | Wholesale & retail | 2025 |
| Allianceuk Limited | Wholesale & retail | 2002 |
| Alliantist Holdings Limited | Financial services | 2017 |
| Alliantist Limited | Information & communication | 2003 |
| Allied Land Limited | Real estate | 1984 |
| Allied Telecommunications Limited | Information & communication | 2020 |
| Alliot Bond Consultants Ltd | Health & social care | 2025 |
| Allison Jeffery Laser and Skin Clinic Limited | Health & social care | 2017 |
| Allison Jeffery Skin Health Clinic Limited | Health & social care | 2015 |
| Allnaturals Limited | Wholesale & retail | 2018 |
| Allogenrx Ltd. | Administrative & support | 2013 |
| Allround Property Services Ltd | Construction | 2024 |
| Allsee Global Ltd | Information & communication | 2019 |
| Allserve Maintenance Solutions Limited | Construction | 2026 |
| Allsop Kane and Allen Limited | Financial services | 2012 |
| Allstar Commercials Limited | Wholesale & retail | 2021 |
| Allum Associates Limited | Professional & scientific | 1978 |
| Allum Builders Limited | Construction | 2008 |
| Allure Adornments Ltd | Construction | 2023 |
| Alma Developments (Sussex) Ltd | Construction | 2024 |
| Alma Sales Group Ltd | Administrative & support | 2020 |
| Alma Studio - Tattooing Ltd | Other services | 2022 |
| Alma's Alterations Ltd | Other services | 2025 |
| Almael Trade Ltd | Hospitality | 2024 |
| Almond Capital Limited | Extraterritorial | 2012 |
| Almond Property Limited | Administrative & support | 1999 |
| Alonglines Limited | Arts & recreation | 2005 |
| ALP Leisure Ltd. | Hospitality | 1997 |
| Alpha & Omega Consultancy Ltd | Other services | 2013 |
| Alpha a Sourcing Ltd | Administrative & support | 2018 |
| Alpha Asset Management Ltd | Real estate | 2022 |
| Alpha Beta Group Limited | Wholesale & retail | 2020 |
| Alpha Brighton Properties Ltd | Real estate | 2023 |
| Alpha Green Solutions (Southern) Trading Ltd | Construction | 2025 |
| Alpha Healthcare Solutions Ltd | Wholesale & retail | 2014 |
| Alpha Sky Ltd | Real estate | 2022 |
| Alpha Workshop Ltd | Hospitality | 2023 |
| Alphaes Limited | Information & communication | 2024 |
| Alphagal Ltd | Arts & recreation | 2024 |
| Alphamove Removals Ltd | Transport & logistics | 2018 |
| Alphanet Media Limited | Professional & scientific | 2002 |
| Alphaocean.Ai Ltd | Transport & logistics | 2019 |
| Alphen Design Ltd | Professional & scientific | 2025 |
| Alpina Systems Limited | Professional & scientific | 1994 |
| Alpine Child Care Ltd | Administrative & support | 2012 |
| Alpine Infusion Ltd | Administrative & support | 2000 |
| Alpine Property Associates Ltd | Households | 2023 |
| Alpine Technology Ltd. | Wholesale & retail | 1994 |
| Alright Mucka Limited | Information & communication | 2025 |
| Alrousan Enterprises Ltd | Wholesale & retail | 2010 |
| ALS Associates Limited | Professional & scientific | 2013 |
| Alstons Surgical Company Limited | Real estate | 1947 |
| ALT Outdoors Ltd | Hospitality | 2026 |
| Altan Fish and Chips Ltd | Hospitality | 2024 |
| Alter&Company Ltd | Professional & scientific | 2016 |
| Alternative Endings Productions Ltd | Information & communication | 2014 |
| Alternox Scientific Ltd | Professional & scientific | 2020 |
| Altitude Accountants Limited | Professional & scientific | 2019 |
| Altnet Solutions Ltd | Information & communication | 2020 |
| Alto Edge Consulting Ltd | Professional & scientific | 2025 |
| Alto Films Ltd | Information & communication | 1996 |
| Alto LAB Ltd | Extraterritorial | 2016 |
| Altura Data Ltd | Information & communication | 2025 |
| Alucia Ltd | Financial services | 2025 |
| Alun Callender Photography Limited | Arts & recreation | 2015 |
| Alva & ME Limited | Real estate | 2025 |
| Alvarium Home Reit Advisors Limited | Financial services | 2020 |
| Always Adventure Ltd | Administrative & support | 2014 |
| Always Available Vehicles Limited | | 1983 |
| Always Possible Limited | Professional & scientific | 2015 |
| AM General Building (Brighton) Ltd | Construction | 2023 |
| AM Global Specialist Consulting Limited | Professional & scientific | 2020 |
| AM PM Property Management Ltd | Households | 2024 |
| AM Solutions Couriers & Logistics Ltd | Transport & logistics | 2023 |
| AMA Coaching Limited | Health & social care | 2021 |
| AMA Imperial Ltd | Real estate | 2026 |
| Amaberry Ltd | Hospitality | 2018 |
| Amadablam Health Ltd. | Health & social care | 2015 |
| Amanah Executive Services Ltd | Professional & scientific | 2015 |
| Amanara (UK) Limited | Information & communication | 2004 |
| Amanda Heath Art Ltd | Arts & recreation | 2021 |
| Amanda King Limited | Information & communication | 2007 |
| Amanda Lewis Eyecare Ltd | Health & social care | 2025 |
| Amanecer Lifestyle Limited | Wholesale & retail | 2022 |
| Amar News Ltd | Wholesale & retail | 2014 |
| Amaran Limited | Real estate | 2020 |
| Amaryllis Property Limited | Administrative & support | 2002 |
| Amazing Coaching Business Limited | Other services | 2021 |
| Amazing Spaces, Kitchens and Interiors Limited | Wholesale & retail | 2013 |
| Ambakh Ltd | Hospitality | 2012 |
| Ambassador-Line Southern Ltd | Transport & logistics | 2021 |
| Amber Garage Limited | Wholesale & retail | 2014 |
| Amber Home Care Ltd | Health & social care | 2005 |
| Amber Vision Ltd | Administrative & support | 2017 |
| Amberelektron Ltd | Professional & scientific | 2020 |
| Ambermor Solutions Ltd | Professional & scientific | 2013 |
| Ambido Ltd | Construction | 2017 |