| Body Solutions London Ltd | Arts & recreation | 2013 |
| Bofferding Limited | Wholesale & retail | 2026 |
| Boha Events Ltd | Hospitality | 2021 |
| Bokz Limited | Wholesale & retail | 2023 |
| Bolger & Sons Plastering Ltd | Construction | 2025 |
| Bolt Exec Limited | Administrative & support | 2024 |
| BON Appetit Group London Limited | Administrative & support | 2020 |
| BON BON Plant Based Ltd | Wholesale & retail | 2023 |
| Bonbon Trading Limited | Wholesale & retail | 2004 |
| Bonneycourt Limited | Health & social care | 1993 |
| Booberry Limited | Real estate | 2020 |
| Bookworm Management Limited | Wholesale & retail | 2002 |
| Bootcamp Pilates Ltd | Arts & recreation | 2010 |
| Booth Motion Ltd | Information & communication | 2018 |
| Boots Media Limited | Professional & scientific | 2023 |
| Boppin' Bunnies Limited | Arts & recreation | 2007 |
| Bora Bora Boutique Ltd | Wholesale & retail | 2016 |
| Boreham Fish Ltd | Hospitality | 2015 |
| Boreham Holt Management Limited | Households | 1965 |
| Boreham Properties Limited | Real estate | 2017 |
| Boreham Wood & Elstree Community Radio Ltd | Information & communication | 2023 |
| Boreham Wood Football Club Limited | Arts & recreation | 1990 |
| Borehamwood 2000 FC Limited | Arts & recreation | 2015 |
| Borehamwood Dental Practice Ltd | Health & social care | 2010 |
| Borehamwood Enterprise Centre Management Limited | Households | 1997 |
| Borehamwood Food & Wine Ltd | Wholesale & retail | 2025 |
| Borehamwood Fruit and Vegtables Limited | Wholesale & retail | 2023 |
| Borehamwood Kosher Food Group Limited | Hospitality | 2017 |
| Borehamwood Ortho Clinic Limited | Health & social care | 2009 |
| Borehamwood Rail Ltd | Professional & scientific | 2024 |
| Borehamwood Restaurant Ltd | Hospitality | 2019 |
| Borehamwood Trading Ltd | Hospitality | 2021 |
| Borehamwood Youth Football Club Limited | Arts & recreation | 2006 |
| Borg IT Limited | Information & communication | 2021 |
| Borgen Limited | Real estate | 2014 |
| Born 2 Boogie Ltd | Arts & recreation | 2024 |
| Boro Pizza Linthorpe Ltd | Hospitality | 2024 |
| Boslan Group Limited | Professional & scientific | 2024 |
| Bosphorus Consulting Ltd | Professional & scientific | 2020 |
| BOT Drylining Limited | Construction | 2014 |
| Boulters Meadow Residents Management Company Limited | Households | 2012 |
| Bounty Transportation LLP | | 2015 |
| Bourne Hall Residents Limited | Households | 1988 |
| Bousoug Interactive Ltd | Information & communication | 2010 |
| Boustead Capital Markets LLP | | 2018 |
| Boutique Hotel Club Ltd | Administrative & support | 2009 |
| Bowman & Co. Lettings Limited | Real estate | 1997 |
| Bowman & Company (Software) Limited | Professional & scientific | 1985 |
| Bowman Electrical Contractors Limited | Construction | 2007 |
| Box Clever Fitness Limited | Education | 2025 |
| Box Tree Clinic Limited | Health & social care | 2016 |
| BOX2PACK Ltd | Administrative & support | 2021 |
| Boxer 10 Investments Limited | Real estate | 2016 |
| Boxer 100 Investments Limited | Real estate | 2017 |
| Boxer 18 Investments Limited | Real estate | 2021 |
| Boxer 25 Investments Ltd | Real estate | 2014 |
| Boxer 26 Investments Limited | Real estate | 2020 |
| Boxer 36 Investments Limited | Real estate | 2017 |
| Boxer 360 Investments Limited | Real estate | 2020 |
| Boxr Holdings Limited | Arts & recreation | 2018 |
| Boyne Publicity Limited | Professional & scientific | 1997 |
| Bpacl Accountancy Services Limited | Professional & scientific | 2017 |
| Bpacl Limited | Professional & scientific | 2018 |
| BPG (UK) Limited | Administrative & support | 2006 |
| Bpje Ltd | Administrative & support | 2025 |
| Bpsc Limited | Construction | 2011 |
| Bracknell Development Limited | Real estate | 2018 |
| Braganza Street (Management Company) Limited | Households | 2023 |
| Brainstorms Projects Ltd | Arts & recreation | 2024 |
| Braintree Dental Holding Limited | Health & social care | 2025 |
| Braintree Development Ltd | Real estate | 2018 |
| Braithwaites Chauffeurs Limited | Transport & logistics | 2017 |
| Brambling Close Residents Limited | Households | 2000 |
| Branco Property Ltd | Real estate | 2025 |
| Branded Accessories Limited | Wholesale & retail | 2017 |
| Brandmart UK Limited | Administrative & support | 2024 |
| Brandspulse Limited | Other services | 2018 |
| Bravado Clothing Ltd | Manufacturing | 2025 |
| Bray Facilities LLP | | 2016 |
| BRE Ilford Limited | Financial services | 2021 |
| Breadbyae Ltd | Manufacturing | 2025 |
| Breakdown Recovery Ltd | Transport & logistics | 2020 |
| Breamcrest Limited | Hospitality | 1990 |
| Breath Insight Ltd | Manufacturing | 2025 |
| Breathsense Limited | Manufacturing | 2022 |
| Breed Above Limited | Administrative & support | 2007 |
| Breega UK Limited | Professional & scientific | 2020 |
| Brenner Productions Limited | Professional & scientific | 2002 |
| Brentano Suite Primrose Hill Limited | Administrative & support | 2018 |
| Brentrack Limited | Real estate | 2018 |
| Brexa Limited | Financial services | 2001 |
| Brezza Entertainment Ltd | Arts & recreation | 2021 |
| Brian J Hyman (Holdings) Limited | Financial services | 1970 |
| Brian Timoney Actors Studio Limited | Administrative & support | 2008 |
| Brick Productions Ltd | Information & communication | 2008 |
| Brickman Consulting Ltd | Professional & scientific | 2022 |
| Bridge Cross Care Ltd | Health & social care | 2011 |
| Bridge Line Technology Ltd | Wholesale & retail | 2016 |
| Bridged Networks Ltd | Information & communication | 2013 |
| Bridging Mountains Limited | Professional & scientific | 2024 |