| Auto Shine Flash Ltd | Construction | 2022 |
| Autobase Film Services Limited | Transport & logistics | 2019 |
| Automart UK Limited | Wholesale & retail | 2019 |
| Automated Installation Solutions Limited | Manufacturing | 2018 |
| Automatos Solutions Ltd | Professional & scientific | 2023 |
| Automotive Innovations (ST Albans) Limited | Administrative & support | 2008 |
| Automotive Innovations (ST. Albans) Holdings Limited | Financial services | 2016 |
| Autonest Ltd | Administrative & support | 2026 |
| Autos Xcel Ltd | Wholesale & retail | 2025 |
| AUTOSCOUT48 Limited | Wholesale & retail | 2017 |
| Autotech UK (Herts) Limited | Wholesale & retail | 2013 |
| Autoworks Limited | Real estate | 1995 |
| Auxilium Limited | Information & communication | 2018 |
| AV Cybersec Ltd | Information & communication | 2024 |
| Avakkado Ltd | Information & communication | 2026 |
| Avamj Properties Limited | Real estate | 2020 |
| Avantogen Holdings Ltd | Financial services | 2017 |
| Avebury Court Management Company Limited | Real estate | 1986 |
| Avedis (Ruislip) Management Company Limited | Households | 2016 |
| Aventive Systems Ltd | Information & communication | 2024 |
| Aventure Audio Visual Ltd | Information & communication | 2024 |
| Avenue Court Residents' Association Limited | Real estate | 2007 |
| AVF Transit Ltd | Transport & logistics | 2016 |
| Avianz Asset Management Limited | Financial services | 2018 |
| Aviation UK Marketing and Sales Ltd | Professional & scientific | 2025 |
| Aviela Skincare Limited | Manufacturing | 2017 |
| Avocado Marketing & Consulting Limited | Professional & scientific | 2012 |
| Avondale (Cressing) Management Company Limited | Households | 2017 |
| Avonleam Limited | Professional & scientific | 2012 |
| AVP Trader Ltd | Manufacturing | 2021 |
| Avramsportsmanagement Ltd | Arts & recreation | 2024 |
| Avury Ltd | Wholesale & retail | 2020 |
| AVV Developments Limited | Construction | 2025 |
| AVV Properties Ltd | Administrative & support | 2017 |
| AVV Solutions Limited | Construction | 1996 |
| AVY Consulting Limited | Information & communication | 2008 |
| AVY Properties Limited | Real estate | 2017 |
| AW & Co Limited | Professional & scientific | 2013 |
| AW Gillies Consultancy Limited | Professional & scientific | 2007 |
| AW Mobile Motoring Services Ltd | Wholesale & retail | 2026 |
| Away Breaks Limited | Administrative & support | 2022 |
| Away Resorts (Transport) Limited | Transport & logistics | 2008 |
| Away Resorts Holdings Limited | Hospitality | 2008 |
| Away Resorts Limited | Hospitality | 2007 |
| Awchilds Ltd | Real estate | 2014 |
| AWD International Ltd | Wholesale & retail | 2016 |
| Awdp Ltd | Real estate | 2022 |
| Awel Y MOR Pwllheli Management Company Limited | Households | 2014 |
| Awesome Foursome Limited | Extraterritorial | 2016 |
| AXE Academy Limited | Arts & recreation | 2025 |
| Axile Solutions Ltd | Information & communication | 2023 |
| Axiom Care Group Ltd | Financial services | 2022 |
| Axiom Care Ltd | Health & social care | 2020 |
| Axiom Care Support Limited | Professional & scientific | 2016 |
| Axiom Home Care Limited | Health & social care | 2020 |
| Axis Consulting Ltd | Professional & scientific | 2010 |
| Axis Pharma Limited | Professional & scientific | 2004 |
| Axonics Modulation Technologies, U.K. Limited | Professional & scientific | 2015 |
| Axonics Women's Health Limited | Manufacturing | 1996 |
| Axra Ltd | Wholesale & retail | 2026 |
| Axterix Removals Ltd | Transport & logistics | 2025 |
| Ayla Tree Care Ltd | Professional & scientific | 2016 |
| Aymlax Ltd | Information & communication | 2025 |
| AYO Oyebade Consultancy Limited | Information & communication | 1990 |
| AYO Oyebade Productions Limited | Professional & scientific | 2008 |
| Ayurvera Limited | Health & social care | 2017 |
| Azalea (Alton) Leasehold Management Company Limited | Households | 2019 |
| Azalea (Medstead) Leasehold Management Company Limited | Households | 2018 |
| Azalea (Medstead) Management Company Limited | Households | 2017 |
| Azamcx Limited | Health & social care | 2013 |
| Azis London Ltd | Hospitality | 2025 |
| Azkon Ltd | Financial services | 2020 |
| Azkonstruct Ltd | Construction | 2020 |
| Azmini Consulting Ltd | Construction | 2018 |
| Aztek Electrical Services Ltd | Construction | 2026 |
| Azure Seas Limited | Hospitality | 2018 |
| Azwall Ltd | Construction | 2021 |
| B & B Radio & TV Limited | Wholesale & retail | 2011 |
| B & M Care Group Limited | Professional & scientific | 1986 |
| B & M Hemel LLP | | 2007 |
| B & M Residential Care Limited | Professional & scientific | 1991 |
| B H Commercial Construction Ltd | Construction | 2019 |
| B Hair & Beauty Ltd | Other services | 2019 |
| B Lawrence Consultancy Ltd | Professional & scientific | 2010 |
| B Z Premier Ltd | Real estate | 2016 |
| B&N Financial Planning Limited | Financial services | 2017 |
| B-Safe Scaffold Ltd | Construction | 2025 |
| B.B.G. Building Ltd | Construction | 2018 |
| B.C Surveying Hertfordshire Ltd | Professional & scientific | 2021 |
| B.D.S Painting Contractors Limited | Construction | 2011 |
| B.E.E. Caterers Ltd | Hospitality | 2025 |
| B91 Management Company Limited | Households | 2006 |
| BA Entertainment Services Ltd | Arts & recreation | 2025 |
| Baba Spice Restaurant Limited | Hospitality | 2016 |
| Babymoon Ltd | Health & social care | 2022 |
| Backlight & Smoke Ltd | Information & communication | 2011 |
| BAD Pony Ltd | Wholesale & retail | 2026 |
| Badbury Reach Management Company Limited | Households | 2020 |
| Badgearts Limited | Wholesale & retail | 2017 |
| Bahar 2016 Ltd | Extraterritorial | 2017 |