| Abbotsford Lodge Management Limited | Households | 1963 |
| ABJ Training Limited | Education | 2012 |
| ABN Ltd | Construction | 2016 |
| Abode Realty Services Limited | Real estate | 2019 |
| Abode Resources Limited | Real estate | 2025 |
| ABS Investments Holdings Ltd | Financial services | 2018 |
| ABV UNO Limited | Real estate | 2022 |
| Acacia Care (Broadnook) Ltd | Health & social care | 2025 |
| Acacia Care (Burton) Ltd | Health & social care | 2024 |
| Acacia Care (Chesterfield) Ltd | Health & social care | 2020 |
| Acacia Care (Hinckley) Ltd | Health & social care | 2022 |
| Acacia Care (Hunstanton) Ltd | Health & social care | 2023 |
| Acacia Care (Kingsway) Ltd | Health & social care | 2020 |
| Acacia Care (MH) Ltd | Health & social care | 2019 |
| Acacia Care (NL) Ltd | Health & social care | 2023 |
| Acacia Care (Nottingham) Ltd | Health & social care | 2013 |
| Acacia Care (Peterborough) Ltd | Health & social care | 2025 |
| Acacia Care (Radcliffe) Ltd | Health & social care | 2025 |
| Acacia Care (Rickmansworth) Ltd | Administrative & support | 2017 |
| Acacia Care Holdings Ltd | Health & social care | 2019 |
| Acacia Care Investments Ltd | Health & social care | 2017 |
| Acacia Properties (BO) Ltd | Real estate | 2020 |
| Accident Repair Centre Uxbridge Limited | Professional & scientific | 2022 |
| Accountancy Gateway Ltd | Professional & scientific | 2010 |
| Accuedge Ltd | Information & communication | 2024 |
| Ace Cars Express (Northwood) Limited | Transport & logistics | 2011 |
| Ace Cars Northwood Limited | Transport & logistics | 2026 |
| Ace Density Ltd | Other services | 2026 |
| Aces Fans Ltd | Manufacturing | 1969 |
| Achievers Consulting Ltd | Professional & scientific | 2014 |
| Aclonyx Ltd | Information & communication | 2026 |
| Acmco Ltd | Professional & scientific | 2014 |
| Acorn Business Consultancy Ltd | Administrative & support | 2019 |
| Acorn Capital Properties Ltd | Real estate | 2021 |
| Acorns Investments Limited | Real estate | 2012 |
| Acquired Knowledge Limited | Professional & scientific | 2014 |
| Acre Invest (Sydenham) Limited | Real estate | 2016 |
| Across the Universe Ventures Limited | Professional & scientific | 2021 |
| Action Audio Visual Limited | Administrative & support | 1992 |
| Active Sonic Technologies UK Limited | Information & communication | 2024 |
| Active Tennis Limited | Education | 2012 |
| Actum Ventures Limited | Professional & scientific | 2006 |
| Adam Wales Associates Ltd | Real estate | 2020 |
| Adams Place Ltd | Hospitality | 2023 |
| ADB2 Limited | Construction | 2025 |
| Adelphi Secretaries Limited | Professional & scientific | 1961 |
| Adept Payments Limited | Information & communication | 2016 |
| Admiral Real Estates Limited | Real estate | 2015 |
| Ados Contractors Limited | Construction | 2006 |
| Adrian C Mansbridge & Company Ltd | Professional & scientific | 2014 |
| ADRIYA1 Solutions Ltd | Financial services | 2018 |
| Advantix Limited | Professional & scientific | 2002 |
| Advantix Services Ltd | Professional & scientific | 2024 |
| Adya Properties Ltd | Real estate | 2024 |
| Aegle Solutions Limited | Real estate | 2011 |
| Aerec Limited | Administrative & support | 2012 |
| Aerie Properties Ltd | Real estate | 2017 |
| Aerilon Ltd | Arts & recreation | 2025 |
| Aeris Airport Transfers Ltd | Administrative & support | 2026 |
| Aesthetic Amore Limited | Other services | 2022 |
| Aesthetics and Beauty Salon Ltd | Other services | 2024 |
| Afghan Heritage Events Ltd | Hospitality | 2025 |
| Afrikwa Ltd | Manufacturing | 2017 |
| AFT (the Grand) LLP | | 2015 |
| AFT (Tooting) LLP | | 2015 |
| After US, Separation and Divorce Ltd | Information & communication | 2023 |
| AGG Investments Ltd | Real estate | 2000 |
| Agile Capital Limited | Construction | 2019 |
| Aglo Tech Limited | Real estate | 2025 |
| Ahavah Healthcare Limited | Health & social care | 2008 |
| Ahimsa Vegan Ltd | Hospitality | 2016 |
| Aidentity Studio Ltd | Professional & scientific | 2020 |
| Aintelope UK Limited | Information & communication | 2026 |
| Aisiki Accommodation Limited | Real estate | 2017 |
| Aisiki Investments Limited | Real estate | 2017 |
| Aisiki Living Limited | Real estate | 2016 |
| Aisiki Stays Limited | Real estate | 2015 |
| AJ Padel Ltd | Wholesale & retail | 2024 |
| Ajnish Limited | Professional & scientific | 1998 |
| AK & AK Properties Limited | Real estate | 2026 |
| Akatan Investments Ltd | Financial services | 2019 |
| Akeman Business Park Limited | Real estate | 2015 |
| Akeso Estates Ltd | Real estate | 2020 |
| AKM Creative Consulting Ltd | Professional & scientific | 2024 |
| Akrb Properties Limited | Real estate | 2024 |
| Akshardham Funeral Directors Limited | Other services | 2019 |
| Akta & Jaymala Patel Limited | Real estate | 2022 |
| AL Group Ltd | Financial services | 2021 |
| Al-Rayan Consultants Limited | Real estate | 2018 |
| Alan BEE Properties Limited | Administrative & support | 2002 |
| Alan Goldsman Limited | Professional & scientific | 2014 |
| Albemarle Glasgow 2012 LLP | | 2012 |
| Albert Huber Limited | Agriculture & fishing | 2003 |
| Aldgate Builders Limited | Construction | 2025 |
| Aldis House Freehold Management Co. Limited | Real estate | 2026 |
| Alex Holder Editorial Limited | Administrative & support | 2017 |
| Alex Howe Photography Limited | Professional & scientific | 2013 |
| Alexander Coaching LLP | | 2014 |
| Alexander Court 91 Ducks Hill Road Limited | Administrative & support | 2019 |
| Alfred Ashley Group Limited | Information & communication | 1996 |