| Athena FI Limited | Transport & logistics | 2017 |
| Atlantic Customer Solutions Limited | Information & communication | 2005 |
| Atlas Palmer Limited | Professional & scientific | 2024 |
| Atlas Safety Group Limited | Professional & scientific | 1991 |
| Attica Holdings Limited | Financial services | 2020 |
| Attis Technology Limited | Information & communication | 2017 |
| Attitude Smiles Ltd | Health & social care | 2021 |
| Attunity GTM Ltd | Professional & scientific | 2026 |
| Aubert Business Consulting Ltd | Professional & scientific | 2010 |
| Audiohire Ltd. | Administrative & support | 2014 |
| Aurion Energy Ltd | Professional & scientific | 2011 |
| Aurrenhub Ltd | Construction | 2025 |
| Austin Electrical Ltd | Construction | 2002 |
| Authority Software Limited | Information & communication | 2010 |
| Autoalex Limited | Information & communication | 2021 |
| Autocraft Repairs Limited | Wholesale & retail | 2012 |
| Automated Blinds and Awnings Limited | Construction | 2008 |
| Avalon Cellars Two Limited | Professional & scientific | 2007 |
| Avast Developments Limited | Real estate | 2007 |
| Avatar Management Limited | Professional & scientific | 1996 |
| Avent Roofing Services Ltd | Construction | 2015 |
| Avery Cole Limited | Real estate | 2024 |
| Aviasafe UK Limited | Wholesale & retail | 2024 |
| Avila Trading Ltd | Hospitality | 2019 |
| Avoca Ltd | Administrative & support | 2024 |
| AW Electrical Services Ltd | Construction | 2015 |
| AWB Laboratories Limited | Administrative & support | 2000 |
| AWBWMC2 Limited | Construction | 2010 |
| Awjc Properties Ltd | Real estate | 2022 |
| Axiom Brands Limited | Wholesale & retail | 2013 |
| Axiom Insights Ltd | Information & communication | 2014 |
| Axios Security Solutions Ltd | Administrative & support | 2024 |
| Ayai Group Holdings Ltd | Financial services | 2026 |
| Aylesbay Windows Limited | Professional & scientific | 1920 |
| Aztec Consulting Ltd | Information & communication | 2018 |
| Azucena & Co. Ltd | Professional & scientific | 2024 |
| B & H Investments Limited | Real estate | 2006 |
| B & N Europe Limited | Professional & scientific | 2015 |
| B & S Fruits Limited | Wholesale & retail | 1981 |
| B Cook Electrical Limited | Construction | 2018 |
| B&M Electric Ltd | Construction | 2026 |
| B&R Business Solutions Limited | Administrative & support | 2018 |
| B&S Plumbing and Heating Limited | Construction | 2017 |
| B.C.E. Mills Bros. and Partners Co. Limited | Construction | 1974 |
| B1 Solutions Limited | Information & communication | 2007 |
| B2B Email KIT Limited | Information & communication | 2023 |
| Baba Fried Chicken Limited | Hospitality | 2016 |
| Baboohan (Nominee) Limited | Financial services | 2015 |
| Babysigners Limited | Education | 2010 |
| Backing British Business Ltd | Financial services | 2014 |
| Backstabbers Limited | Administrative & support | 2026 |
| Bade Properties Limited | Real estate | 2018 |
| Baker Freight Ltd | Transport & logistics | 2025 |
| Baker Street Drycleaners Ltd | Other services | 2014 |
| Balfour Road Management Company Limited | Administrative & support | 2006 |
| Bamford Films Ltd | Information & communication | 2021 |
| Banat Consultants Ltd | Professional & scientific | 2020 |
| Bandstop Limited | Professional & scientific | 2012 |
| Banksy Limited | Information & communication | 2015 |
| Barjeel Ltd | Real estate | 2021 |
| Barmbeck Limited | Professional & scientific | 2020 |
| Barn Energy Limited | Construction | 2012 |
| Barnfield Holdings Limited | Professional & scientific | 2018 |
| Baronsclere Court Residents Association Limited | Households | 1984 |
| Barratt & Robinson (1877) Limited | Extraterritorial | 1986 |
| Basar Investment Limited | Real estate | 2025 |
| Bass Rock (South) Consulting Limited | Professional & scientific | 2014 |
| Bateleur Ltd | Information & communication | 2017 |
| Bathsheba Bay Limited | Education | 2015 |
| Batson Legal Ltd | Professional & scientific | 2022 |
| Baxter & Gillon Ltd | Professional & scientific | 2020 |
| Baxter Thompson Ltd. | Professional & scientific | 2009 |
| Bayley Developments Ltd | Real estate | 2023 |
| BB Bookkeepers Crunch Ltd | Professional & scientific | 2021 |
| Bbbi Limited | Professional & scientific | 2017 |
| BC Hotel Limited | Hospitality | 2024 |
| BCC Consultancy Ltd | Information & communication | 2021 |
| BCS Plumbing Limited | Construction | 2007 |
| BDH Centreless Limited | Manufacturing | 2002 |
| BE Office Investments Ltd | Real estate | 2019 |
| BE Offices (Watford) Ltd | Real estate | 2023 |
| Beach Media Limited | Administrative & support | 2012 |
| Beacon House Consultancy Ltd | Administrative & support | 2006 |
| Beagle HR Ltd | Professional & scientific | 2019 |
| Bean & Beyond Limited | Hospitality | 2024 |
| Bear Property LLC Ltd | Real estate | 2024 |
| Beards Awnings & Verandas Limited | Manufacturing | 2026 |
| Beards Blinds & Awnings Ltd | Manufacturing | 2013 |
| Beardygoat Ltd | Information & communication | 2016 |
| Beata Soroko Skincare Solutions Ltd | Other services | 2019 |
| Beatmondays Limited | Information & communication | 2018 |
| Beato Consulting Limited | Information & communication | 2020 |
| Beats Learning Limited | Education | 2014 |
| Beatson Clark (Trustees) Limited | Professional & scientific | 1980 |
| Beaufort Green Holdings Limited | Financial services | 2025 |
| Beaufort Green London Limited | Real estate | 2024 |
| Beauforts Motivational Intelligence Limited | Other services | 2015 |
| Beauty and the Lease Management Ltd | Real estate | 2025 |
| Beauty Secrets Limited | Administrative & support | 2008 |
| Beauty Secrets Salon and Spa Limited | Administrative & support | 2008 |