| Apache Locations & Logistics Limited | Information & communication | 2020 |
| APL Media AI Limited | Financial services | 2024 |
| APL Media Group Limited | Financial services | 2018 |
| APL Media Limited | Information & communication | 1997 |
| Apsley Support Services Limited | Administrative & support | 2007 |
| APW & Sons Limited | Construction | 2014 |
| Aqipa United Kingdom Limited | Wholesale & retail | 2018 |
| Aquathirst UK Ltd | Hospitality | 2026 |
| Arago Property Limited | Real estate | 2026 |
| ARC Inflight Dining Limited | Hospitality | 2024 |
| Argon International Solutions Holdings Limited | Professional & scientific | 2023 |
| Argon International Solutions Ltd | Professional & scientific | 2019 |
| Arias Holdings Limited | Real estate | 2018 |
| Arkon Ltd | Professional & scientific | 2002 |
| Aromont U.K. Limited | Wholesale & retail | 1986 |
| Arthur Money Ltd | Financial services | 2023 |
| Artisan Properties (Harrow) Limited | Real estate | 2020 |
| Artisan Properties (Herts) Limited | Real estate | 2023 |
| Artisan Solutions UK Limited | Other services | 2008 |
| Artistico UK Ltd | Construction | 2013 |
| Ases Investments Ltd | Real estate | 2026 |
| ASH Grove Lettings Ltd | Real estate | 2022 |
| Assetpool Ltd | Professional & scientific | 2019 |
| Assured Shine Ltd | Administrative & support | 2021 |
| Astoncrown Limited | Real estate | 1983 |
| Aurora Creation Studios Limited | Information & communication | 2026 |
| Auto Fast Repair Ltd | Wholesale & retail | 2023 |
| Auto Motive Service & Repair Ltd | Wholesale & retail | 2009 |
| Autolink Concessionaires (A19) Limited | Construction | 2000 |
| Autolink Concessionaires (M6) PLC | Construction | 1996 |
| Autolink Holdings (A19) Limited | Professional & scientific | 2000 |
| Autolink Holdings (M6) Ltd | Construction | 1997 |
| Automation AI Ltd | Manufacturing | 2022 |
| Awesome Lishy Limited | Information & communication | 2015 |
| Axis Land Partnerships Limited | Construction | 2016 |
| B K S Energy Limited | Energy | 2010 |
| Backbone 2 Business Ltd | Administrative & support | 2009 |
| Badgerand Ltd | Professional & scientific | 2022 |
| Bakes Cake and Coffee Ltd | Hospitality | 2021 |
| Balantyne Management Limited | Professional & scientific | 2021 |
| Ballet Nights 2023 Limited | Arts & recreation | 2023 |
| Ballet Nights New Voices 2024 Limited | Arts & recreation | 2024 |
| Ballyross Energy Storage Limited | Energy | 2024 |
| Balstone Holdings Limited | Financial services | 2022 |
| Balstone Investments Limited | Real estate | 2022 |
| Baltic Gladiator Power Ltd | Health & social care | 2024 |
| Bankside Electrical Contractors Limited | Construction | 1970 |
| Bantide Ltd | Construction | 2025 |
| Barlborough Limited | Energy | 2012 |
| Barnet Scaffolding Services Limited | Construction | 2007 |
| Barnsway Residents Association Limited | Households | 2009 |
| Batchworth Limited | Wholesale & retail | 2004 |
| Batsworthy Cross Wind Farm Limited | Energy | 2014 |
| BB MOT Centre Ltd | Wholesale & retail | 2025 |
| BE Yourself Academy Ltd | Education | 2025 |
| Bea's Coffee Barn Ltd | Hospitality | 2025 |
| Beale Halai Limited | Construction | 2017 |
| Beale Halai Properties Limited | Real estate | 2019 |
| Bean Here Ltd | Wholesale & retail | 2020 |
| Beane Energy Limited | Energy | 2023 |
| Bear Plant and Machinery Limited | Manufacturing | 2015 |
| Beatselecta Limited | Information & communication | 2007 |
| Beauty Retreat Lounge Ltd | Other services | 2026 |
| Beaver & Grouse Ltd | Professional & scientific | 2023 |
| BEE Clinical Consultancy Ltd | Professional & scientific | 2023 |
| Belbridge Developments Limited | Construction | 2015 |
| Benson Associates Limited | Professional & scientific | 2019 |
| Berkeley Developers Ltd | Construction | 2024 |
| Berteva Hospitality Ltd | Hospitality | 2025 |
| Betsy Lettings Limited | Real estate | 2021 |
| Beyond Accounting Limited | Professional & scientific | 2009 |
| BG Bidco 24 Limited | Financial services | 2025 |
| BG Lower Midco 24 Limited | Financial services | 2025 |
| BG Topco 24 Limited | Financial services | 2025 |
| BG Upper Midco 24 Limited | Financial services | 2025 |
| BH Bookkeeping Ltd | Professional & scientific | 2013 |
| Bhakti Path Ltd | Health & social care | 2025 |
| BHL Groundworks Limited | Construction | 2021 |
| Bilsthorpe Wind Farm Limited | Energy | 2010 |
| Bishop Stortford NPE Ltd | Households | 2023 |
| Bishops DAL Energy Storage Limited | Energy | 2024 |
| Bishopsgate Contracting Services Limited | Administrative & support | 2019 |
| Bishopsgate Employment Services Limited | Administrative & support | 2019 |
| Bishopsgate Group Limited | Administrative & support | 2019 |
| Bite ME Marketing Limited | Professional & scientific | 2022 |
| BJG Hospitality Limited | Hospitality | 2016 |
| BL Wind Limited | Energy | 2013 |
| Black & White Outsourcing Ltd | Financial services | 2005 |
| Black Eagle Property Ltd | Real estate | 2020 |
| Blary Hill Energy Limited | Administrative & support | 2015 |
| Blary Hill Land Limited | Agriculture & fishing | 2019 |
| Bligh & GUY Wedding Visuals Limited | Professional & scientific | 2023 |
| Blok - Building Ltd | Construction | 2020 |
| Blok - Chapel Croft Limited | Real estate | 2020 |
| Blok Design Build Ltd | Real estate | 2013 |
| Blue Moon Bakery Ltd | Hospitality | 2025 |
| Blue Wizard Ltd | Information & communication | 2006 |
| Blueprint Building Consultancy Limited | Professional & scientific | 2026 |
| Blush Lifestyle Limited | Wholesale & retail | 2017 |
| BMB Holdings Limited | Administrative & support | 2017 |