| A Class Tailoring Limited | Other services | 2018 |
| A F Environmental Ltd | Water & waste | 2022 |
| A Fast Cleaning Ltd. | Administrative & support | 2023 |
| A Fast Transport Ltd | Transport & logistics | 2022 |
| A Fish 'N Sea Limited | Wholesale & retail | 2015 |
| A Hair Ltd | Other services | 2023 |
| A Hart Properties Ltd | Real estate | 2022 |
| A J & Michaels Limited | Information & communication | 2014 |
| A J Immigration Services Ltd | Professional & scientific | 2017 |
| A J Legal Services Ltd | Professional & scientific | 2017 |
| A J T Brickwork Ltd | Construction | 2016 |
| A LEE & Sons Building & Groundwork Ltd | Construction | 2019 |
| A Line Developments & Services Ltd | Real estate | 2025 |
| A M Furniture Ltd | Construction | 2017 |
| A M-Gears Ltd | Construction | 2016 |
| A Meacher Ltd | Professional & scientific | 2020 |
| A P Hoyland Electrical Ltd | Construction | 2020 |
| A R C Luton LLP | | 2011 |
| A R Stach Limited | Transport & logistics | 2017 |
| A S Homes Herts Ltd | Construction | 2023 |
| A Smart Change Ltd | Professional & scientific | 2023 |
| A T Amusements Ltd | Arts & recreation | 2024 |
| A Thoughtful Place to BE Ltd | Education | 2017 |
| A Thousand Projects Ltd | Information & communication | 2017 |
| A to Z Bespoke Kitchens Ltd | Construction | 2012 |
| A to Z Building Contractors Ltd | Construction | 2012 |
| A to Z Constructions Solutions Limited | Construction | 2017 |
| A&A Executive Living Ltd | Real estate | 2025 |
| A&A Flooring Ltd | Wholesale & retail | 2014 |
| A&A Studios Ltd | Professional & scientific | 2026 |
| A&C Publications Ltd | Information & communication | 2011 |
| A&G Resourcing Ltd | Administrative & support | 2022 |
| A&G Surveying Ltd | Professional & scientific | 2025 |
| A&M Cars South Ltd | Wholesale & retail | 2015 |
| A&M Drywall Limited | Wholesale & retail | 2022 |
| A&N Team Ltd | Transport & logistics | 2023 |
| A-Concierge Ltd | Administrative & support | 2026 |
| A-L-M Travel Ltd | Transport & logistics | 2013 |
| A-Part Enterprises LLP | | 2014 |
| A-Star Professional Limited | Professional & scientific | 2015 |
| A.A Luxuries Ltd | Wholesale & retail | 2024 |
| A.Force Logistics Limited | Transport & logistics | 2026 |
| A.K.A. Travel Limited | Transport & logistics | 2003 |
| A.S.L Management Consulting Ltd | Construction | 2022 |
| A.T.A. (Engineering Processes) Limited | Wholesale & retail | 1963 |
| A1 Capital Homes Ltd | Real estate | 2023 |
| A1 Equipment Limited | Wholesale & retail | 1992 |
| A1 Health Ltd | Health & social care | 2025 |
| A1 Optician Ltd. | Health & social care | 2011 |
| A1 Premier Transmissions Limited | Wholesale & retail | 2006 |
| A40 Concrete Ltd | Administrative & support | 2022 |
| A40 Grab Hire Limited | Administrative & support | 2020 |
| AA Fireprotect Ltd | Construction | 2025 |
| AAA UK Holdings Ltd | Real estate | 2021 |
| Aaga Limited | Hospitality | 2025 |
| Aaila Restaurant Ltd | Hospitality | 2024 |
| Aake Ltd | Information & communication | 2023 |
| AAL Professional Services Limited | Professional & scientific | 2026 |
| Aanvi Group Limited | Wholesale & retail | 2020 |
| AAR Stores Ltd | Wholesale & retail | 2025 |
| Aarambhmk Ltd | Information & communication | 2026 |
| Aardvark Plumbing & Drainage Limited | Construction | 1998 |
| Aarjay Healthcare Limited | Wholesale & retail | 2010 |
| Aark Travel Ltd | Transport & logistics | 2019 |
| Aarkamint Limited | Arts & recreation | 1996 |
| Aaron's Network Ltd | Information & communication | 2026 |
| Aashiyana Limited | Real estate | 2021 |
| AAY Consulting Services Ltd | Real estate | 2022 |
| AB Bytecrafters Limited | Information & communication | 2025 |
| AB Construction Solution Ltd | Construction | 2023 |
| AB Datum Ltd | Construction | 2022 |
| AB Digital Ltd | Information & communication | 2018 |
| AB Helicopters Ltd. | Transport & logistics | 2012 |
| AB Industrial Trading Ltd | Wholesale & retail | 2016 |
| AB Solar Consulting(Holding) Ltd | Real estate | 2024 |
| AB1 Properties Limited | Financial services | 2018 |
| Abacus Industrial Limited | Wholesale & retail | 2005 |
| Abacus Response Ltd | Construction | 2012 |
| Abana Hemel Ltd | Hospitality | 2023 |
| Abbas Properties and Investment Ltd | Real estate | 2026 |
| Abbathure Flat Management Company Limited | Households | 1994 |
| Abbb Limited | Construction | 2023 |
| Abbew Crew Ltd | Other services | 2024 |
| Abbey Court (Pity ME) Management Company Limited | Households | 2003 |
| Abbey Decorating Limited | Construction | 2014 |
| Abbeyfields (Laughton Common) Management Company Limited | Households | 2004 |
| Abbot's Hill School | Professional & scientific | 2012 |
| Abbots (UK) Limited | Construction | 2004 |
| Abbots Engineering Supplies Limited | Wholesale & retail | 2003 |
| Abbots Limited | Construction | 2024 |
| Abbott Rogers Associates Limited | Information & communication | 2017 |
| ABC Coaching and Consultancy Ltd | Other services | 2016 |
| ABC Consulting Ltd | Other services | 2021 |
| Abcd Transport & Trading Ltd | Transport & logistics | 2021 |
| Abchurch Telecoms Installations Ltd | Information & communication | 2024 |
| Abdul's Property Limited | Real estate | 2025 |
| Abella Finance Solutions Limited | Professional & scientific | 2020 |
| ABG Global Projects Limited | Administrative & support | 2023 |
| ABI Rowley Ltd | Administrative & support | 2019 |
| ABI Town Ltd | Real estate | 2024 |