| Ambay Investments Ltd | Real estate | 2005 |
| AMC Install Limited | Transport & logistics | 2018 |
| AMC UK Engineering Ltd | Construction | 2019 |
| Amega Fleur Home Limited | Other services | 2023 |
| Amen Personnel Healthcare Ltd | Health & social care | 2023 |
| American Professional Nails 264 Ltd | Other services | 2023 |
| American Vehicle Parts Limited | Wholesale & retail | 2007 |
| Amexforce Limited | Construction | 1985 |
| Amiable Consulting UK Ltd | Professional & scientific | 2011 |
| Amigo Support Services Limited | Administrative & support | 2025 |
| Amina Bashir Memorial Trust Limited | Health & social care | 2007 |
| Amor Logistics Ltd | Administrative & support | 2014 |
| Amraaq Limited | Real estate | 2026 |
| Amrg Investments Limited | Real estate | 2020 |
| Amritha Limited | Education | 2005 |
| Amsafur Heritage Ltd | Wholesale & retail | 2026 |
| AMT Electricals Limited | Other services | 2004 |
| AMTRADINGS97 Limited | Wholesale & retail | 2026 |
| AMY Louise Limited | Wholesale & retail | 2001 |
| Anaiah Noelle Beauty Lounge Ltd | Administrative & support | 2016 |
| Analystinfos Ltd | Information & communication | 2025 |
| Anasuya Ltd | Information & communication | 2025 |
| Anbessa Criminal Justice Solutions Limited | Administrative & support | 2003 |
| Anchoi Limited | Wholesale & retail | 2022 |
| Anchor Waterside Management Company Limited | Households | 2004 |
| Anchor Handling Limited | Transport & logistics | 1986 |
| Anchor Point (Block a) RTM Company Limited | Households | 2023 |
| Anchorman Limited | Professional & scientific | 2002 |
| AND Technology Research Limited | Professional & scientific | 1980 |
| Anderson STP Services Ltd | Real estate | 2025 |
| Andmoss Limited | | 1980 |
| Andrew & Company Limited | Wholesale & retail | 1998 |
| Andrew and Fiona Wellington LLP | | 2025 |
| Andrew Hastings Landscape Consultants Limited | Administrative & support | 2002 |
| Andrew J Merritt Limited | Professional & scientific | 2006 |
| Andrew Pearson Engineering Limited | Wholesale & retail | 2005 |
| Andrew Rees Thatching Limited | Construction | 2007 |
| Andy Harragan & SON Limited | Administrative & support | 2005 |
| Andy Hurley Consulting Ltd | Information & communication | 2025 |
| Aneeza and MIM Ltd | Hospitality | 2019 |
| Anfield Property Limited | Real estate | 2021 |
| Angel Wellness Ltd | Health & social care | 2022 |
| Angell Plastering Limited | Construction | 2002 |
| Angies Kebab Limited | Hospitality | 2006 |
| Angle Builders Limited | Construction | 1988 |
| Angleland Limited | | 1980 |
| Anglia Commercial Finance Limited | Financial services | 1991 |
| Anglia Electrical Contractors Limited | | 1988 |
| Anglia Printers Supplies Limited | Manufacturing | 1991 |
| Anglia Ruskin Development Ltd | Real estate | 1992 |
| Anglia Ruskin Enterprise Ltd | Education | 1989 |
| Anglia Self Storage Limited | Administrative & support | 2004 |
| Anglia Tree Surgery Limited | Administrative & support | 2003 |
| Anglian Electrics Limited | Wholesale & retail | 2007 |
| Anglian Environmental Services Limited | Water & waste | 2000 |
| Anglian Valve and Pump Services Ltd | Construction | 2000 |
| Anglo-Net Limited | Wholesale & retail | 1996 |
| Anglobanner Limited | | 1985 |
| Angloshelf Limited | Wholesale & retail | 2007 |
| Angry Beaver Ltd | Wholesale & retail | 2024 |
| Anilam Properties Ltd | Real estate | 2022 |
| Anita Ford Associates Limited | Professional & scientific | 2001 |
| Ankerinn Limited | Hospitality | 2003 |
| ANN E Commerce Limited | Wholesale & retail | 2024 |
| Anness Ltd | Real estate | 2002 |
| Annyka Consulting Ltd | Information & communication | 1998 |
| Ansari Enterprises Limited | Real estate | 2008 |
| Anson Management Company Limited | Real estate | 1986 |
| Anthonium Blessings Ltd | Real estate | 2023 |
| Anthony London Limited | Construction | 1993 |
| Antonio Torres UK Limited | Administrative & support | 2003 |
| Anytime IA Limited | Wholesale & retail | 2024 |
| Aoliyahrahman Limited | Health & social care | 2024 |
| AP Bespoke Estates Limited | Real estate | 2023 |
| AP Moves Ltd | Water & waste | 2025 |
| APA Property Services Limited | Administrative & support | 2001 |
| APA Surveying Limited | Administrative & support | 2006 |
| APD Scaffolding Ltd | Construction | 2021 |
| Apercu Limited | Professional & scientific | 2001 |
| Apex Capital Limited | Professional & scientific | 1997 |
| Apex London Limited | Professional & scientific | 1999 |
| Apex Steel and Aluminium Fabrications Limited | Manufacturing | 2005 |
| Apex Talent Partners Ltd | Education | 2026 |
| Apex Trance Limited | Wholesale & retail | 2025 |
| Apexcommerse Ltd | Wholesale & retail | 2026 |
| Apexion Distributors Ltd | Wholesale & retail | 2025 |
| APG Security and Training Solutions Ltd | Administrative & support | 2021 |
| Apic UK Limited | Manufacturing | 2006 |
| APK Cardiac Services Limited | Health & social care | 1999 |
| APL Mechanical Services Limited | Professional & scientific | 2015 |
| Apollo RPL Limited | Financial services | 2016 |
| Applecheck (Essex) Ltd | Information & communication | 2004 |
| Applered Care Ltd | Health & social care | 2004 |
| Appleyton Limited | Hospitality | 2017 |
| Applicus Limited | Professional & scientific | 2004 |
| Appworks Limited | Information & communication | 2010 |
| Apricot Associates Ltd | Professional & scientific | 2003 |
| April Investments Ltd | Financial services | 2025 |
| APS Bricklaying Contractors Ltd | Construction | 1997 |
| APS Woodford Medical Ltd | Wholesale & retail | 2025 |