| Alard UK Limited | Wholesale & retail | 2026 |
| Alaukick Ltd | Health & social care | 2022 |
| Alba Cafe Limited | Hospitality | 2016 |
| Alba Driving School Ltd | Education | 2010 |
| Albans House Management RTM Company Limited | Households | 2011 |
| Albany Financial Consultants Limited | Financial services | 2004 |
| Albemarle Stirling Limited | Real estate | 2018 |
| Albendji Electrical Limited | Construction | 2018 |
| Albert Wolf Consultancy Limited | Professional & scientific | 2021 |
| Albion Aviation Advisory Ltd | Professional & scientific | 2020 |
| Albion Commercial Cleaning Ltd | Administrative & support | 2018 |
| Albion Court (Bedford Square) Residents Limited | Households | 1991 |
| Albion Glazing Limited | Construction | 2011 |
| Albion Hill LLP | | 2012 |
| Albion Plating Ltd | Manufacturing | 2017 |
| Albion Plumbing Supplies Limited | Wholesale & retail | 2017 |
| Albion Security Ltd | Administrative & support | 2023 |
| Albion Trading GB Limited | Wholesale & retail | 2001 |
| Albion Vape and Beverage Ltd | Wholesale & retail | 2023 |
| Albion Vape Store Ltd | Wholesale & retail | 2024 |
| Albion Window Cleaning Ltd | Administrative & support | 2018 |
| Albus Properties Limited | Real estate | 2025 |
| Alchemy of Worlds Ltd | Education | 2026 |
| Alchemy Realm Limited | Information & communication | 2025 |
| Alchymis Ltd | Manufacturing | 2025 |
| Alcoloco Ltd | Wholesale & retail | 2024 |
| Aldeburn Property (Residents) Company Limited | Households | 1959 |
| Alden R. Bennett Ltd | Wholesale & retail | 2016 |
| Alembis Limited | Information & communication | 2025 |
| Alephbetshin Ltd | Professional & scientific | 2026 |
| Aletheia Education Ltd | Education | 2025 |
| Alex Berwick Ltd | Administrative & support | 2022 |
| Alex Garrett Ltd | Professional & scientific | 2016 |
| Alex Harris Solutions Limited | Professional & scientific | 2016 |
| Alex Mulder Design Ltd | Professional & scientific | 2016 |
| Alex Purkiss Sound Limited | Information & communication | 2023 |
| Alex Riley Ltd | Hospitality | 2018 |
| Alex Young Recruitment Limited | Administrative & support | 2014 |
| Alex's Tyres Limited | Wholesale & retail | 2015 |
| Alexa Sirbu Ltd | Professional & scientific | 2018 |
| Alexander Baxter Construction Limited | Construction | 2025 |
| Alexander Clementine Ltd | Wholesale & retail | 2019 |
| Alexander Home FIX Ltd | Construction | 2024 |
| Alexander Invest Ltd | Financial services | 2018 |
| Alexandr Archive Ltd | Wholesale & retail | 2026 |
| Alexandra Brodski Limited | Information & communication | 2023 |
| Alexandra Rose Charity | Health & social care | 1933 |
| Alexandra Villas (Brighton) Limited | Households | 2008 |
| Alexar Ltd | Transport & logistics | 2021 |
| Alexis Petridis Limited | Administrative & support | 2011 |
| Alexpost Limited | Real estate | 1995 |
| Alfa Carpentry and Building Ltd | Construction | 2018 |
| Alfad Limited | Health & social care | 2019 |
| Alfemax Films Limited | Information & communication | 2006 |
| Alfie & Co Salon Ltd | Other services | 2024 |
| Alfie Hair Ltd | Other services | 2025 |
| Alfin Catering Limited | Hospitality | 2021 |
| Algas Heating & Plumbing Limited | Construction | 2003 |
| Algis Removals Ltd | Transport & logistics | 2025 |
| Algun Limited | Hospitality | 2020 |
| Alhaja Jewellers Limited | Wholesale & retail | 2025 |
| ALI GAS Service Limited | Construction | 2025 |
| ALI the Producer Ltd | Administrative & support | 2017 |
| Alical Ltd | Health & social care | 2025 |
| Alice's Wonderland Ltd | Information & communication | 2024 |
| Alielle Ltd | Real estate | 2017 |
| Align Risk Management Ltd | Professional & scientific | 2022 |
| Align With Francesca Ltd | Professional & scientific | 2022 |
| Align Your Spine Ltd | Information & communication | 2020 |
| Aligned Paediatric Orthopaedic Ltd | Health & social care | 2025 |
| Alihanim Ltd | Hospitality | 2019 |
| Alikate Investments Limited | Real estate | 2022 |
| Aliko Professional Solutions Ltd | Professional & scientific | 2019 |
| Alirity Ltd | Professional & scientific | 2016 |
| Alish Limited | Hospitality | 2020 |
| Alison Jones Coaching Limited | Administrative & support | 2017 |
| Alistair Blue Ltd | Real estate | 2021 |
| Alive Fitness and Natural Health Limited | Arts & recreation | 1990 |
| Aljo Games Ltd | Information & communication | 2020 |
| ALL About Audrey Limited | Wholesale & retail | 2020 |
| ALL About Building Homes Limited | Real estate | 2010 |
| ALL Access Security Ltd | Financial services | 2019 |
| ALL Bikes Electric Ltd | Wholesale & retail | 2020 |
| ALL Brighton Clean Ltd | Administrative & support | 2023 |
| ALL Carpentry Sussex Ltd | Construction | 2023 |
| ALL Conditions Media Ltd | Professional & scientific | 2014 |
| ALL Ears Counselling Ltd | Health & social care | 2017 |
| ALL Grafters Limited | | 1988 |
| ALL in One Solutions Ltd | Construction | 2018 |
| ALL Jobs Pro Ltd | Administrative & support | 2013 |
| ALL Phase Electrical Contractors Limited | Construction | 2016 |
| ALL Possible Futures Ltd | Information & communication | 2019 |
| ALL Service Repairs UK Ltd | Administrative & support | 2018 |
| ALL That Glitters Limited | Wholesale & retail | 2008 |
| ALL Things Brighton Beautiful Limited | Wholesale & retail | 2010 |
| ALL Trades UK (YG) Ltd | Construction | 2015 |
| Allan Farrow Builders Limited | Construction | 1993 |
| Allapplianceservices UK Ltd | Administrative & support | 2018 |
| Allbuilding Ltd | Construction | 2022 |
| Alledecaroan Ltd | Construction | 2026 |