| A1 Hollywood Electrical Limited | Construction | 2007 |
| A1 Payroll Ltd | Professional & scientific | 2013 |
| A1 Premier Services Limited | Information & communication | 2011 |
| A1 Property Limited | Construction | 2015 |
| A2B Freight Logistics Limited | Professional & scientific | 2022 |
| A2B Freight Ltd | Transport & logistics | 2020 |
| A2B Housing Provider Limited | Real estate | 2025 |
| A2B Recruit Ltd | | 2009 |
| A2READ Limited | Education | 2024 |
| A2S Investment Ltd | Real estate | 2022 |
| A3G Capital Limited | Construction | 2025 |
| A3N Investments Ltd | Administrative & support | 2016 |
| A3Z Finance Ltd | Information & communication | 2026 |
| A4 Tech Consulting Ltd | Information & communication | 2026 |
| A45 Building & Landscaping Limited | Construction | 2026 |
| AA & RU Estates Ltd | Real estate | 2023 |
| AA Financial Business Services Ltd | Professional & scientific | 2019 |
| AA Mortgage Services Ltd | Financial services | 2020 |
| AA Ophthalmic Services Ltd | Health & social care | 2016 |
| AA Surveyor Services Ltd | Households | 2024 |
| AA Sutton Diagnostics Limited | Health & social care | 2020 |
| AAA Contracts Ltd | Administrative & support | 2022 |
| AAA Developments Limited | Construction | 2015 |
| Aabour Property Ltd | Real estate | 2022 |
| Aacorn Engineering Limited | Administrative & support | 2012 |
| AAG Corporate Services Ltd | Administrative & support | 2010 |
| AAG Mortgage Brokerage Ltd | Financial services | 1997 |
| AAG Private Clients Limited | Other services | 2005 |
| Aagsjp Limited | Financial services | 2003 |
| Aagw Limited | Wholesale & retail | 2021 |
| AAH Properties Ltd | Real estate | 2016 |
| AAH Wellness Ltd | Arts & recreation | 2026 |
| Aahil Properties Ltd | Real estate | 2020 |
| Aajg Holdings Limited | Construction | 2018 |
| Aalpha Networks Limited | Hospitality | 2016 |
| Aama Limited | Education | 2018 |
| Aamna Asad Limited | Professional & scientific | 2025 |
| AAP Dent Limited | Health & social care | 2024 |
| Aapka Limited | Financial services | 2021 |
| Aardvark Marketing Consultants Ltd | Professional & scientific | 2008 |
| Aarnion Event Management Limited | Other services | 2022 |
| Aarti Ravi Investments Limited | Real estate | 2019 |
| Aartisan CNC Wire Forming Systems Ltd | Manufacturing | 2021 |
| Aask Properties Ltd | Real estate | 2024 |
| AB Electrical Birmingham Ltd | Construction | 2020 |
| AB House Renovation Ltd | Real estate | 2025 |
| AB Sciex UK Limited | Professional & scientific | 2009 |
| AB Spedition Limited | Transport & logistics | 2019 |
| Abaco Property Holdings Limited | Real estate | 2016 |
| Abacus Housing Limited | Hospitality | 2015 |
| Abar Holdings Ltd | Financial services | 2025 |
| Abase-Central Limited | Real estate | 2012 |
| Abbcott Developments Limited | Real estate | 1988 |
| Abbcott Rugby Limited | Real estate | 1995 |
| Abbey Place Management (Coventry) Limited | Households | 2007 |
| Abbey Software Development Limited | Professional & scientific | 2025 |
| Abbeyfield Properties Limited | Construction | 2015 |
| Abbeyfield Society (the) | Hospitality | 1956 |
| Abbeyfield Southport Society Limited (the) | Extraterritorial | 1972 |
| Abbots Salford Caravans Limited | Extraterritorial | 1959 |
| Abbott Medical U.K. Limited | Health & social care | 1989 |
| ABC Education Services Limited | Education | 2015 |
| ABC Electrical Solutions Ltd | Construction | 2018 |
| ABC Management Consultants Ltd | Professional & scientific | 2002 |
| Abdu Ltd | Wholesale & retail | 2025 |
| Abdullah Carpets & Furniture Centre Limited | Wholesale & retail | 2020 |
| ABDULR10-NEUTRAL Ltd | Administrative & support | 2016 |
| Abe-No Ltd | Construction | 2017 |
| Aben Builders Limited | Construction | 2003 |
| Abeo Verto Limited | Professional & scientific | 2010 |
| ABF Invest Ltd | Construction | 2018 |
| ABG WW Ltd | Transport & logistics | 2026 |
| ABHIFEB25 Limited | Transport & logistics | 2025 |
| Abina Holdings Limited | Other services | 2022 |
| Able Personnel UK Limited | Wholesale & retail | 2003 |
| Able Products Limited | Wholesale & retail | 2020 |
| Abode Homes Ltd | Real estate | 2015 |
| Aboutface Publishing Ltd | Information & communication | 2021 |
| Aboutface Training Limited | Health & social care | 2017 |
| Above & Beyond Merchandise UK Limited | Arts & recreation | 2018 |
| Above and Beyond Outsourcing Limited | Administrative & support | 2016 |
| Abri Corporate Services Limited | Real estate | 2019 |
| ABS Installations Ltd | Construction | 2003 |
| ABS Operations Limited | Administrative & support | 2023 |
| ABS Real Estate Limited | Real estate | 2025 |
| ABS Telecommunications Limited | Construction | 2023 |
| Absaara Ltd | Professional & scientific | 2008 |
| Absabe UK Ltd | Construction | 2023 |
| Abshare Share Plan Limited | Other services | 2008 |
| Absolute Yoga Limited | Wholesale & retail | 2018 |
| Absolutely Axelrod Properties Ltd | Real estate | 2019 |
| Abundant Finance Limited | Financial services | 2016 |
| AC Consultants Limited | Information & communication | 2021 |
| AC Electrical Projects Limited | Construction | 2018 |
| AC Plastering Services 2019 Ltd | Construction | 2022 |
| Acacia 2018 Limited | Health & social care | 2018 |
| Academy Projects and Maintenance Limited | Construction | 2025 |
| ACC Equity Ltd | Financial services | 2025 |
| Acce Property Investment Ltd | Real estate | 2025 |
| Accent Wire Limited | Administrative & support | 2006 |