| Black BOY Worldwide Limited | Extraterritorial | 2013 |
| Black Chilli Video Ltd | Information & communication | 2018 |
| Black DOT Investments Limited | Construction | 2018 |
| Black DOT Recruitment Limited | Administrative & support | 2015 |
| Black ELK Productions Ltd | Information & communication | 2020 |
| Black Island Media Limited | Information & communication | 2018 |
| Black LAB Security Ltd | Professional & scientific | 2025 |
| Black OPS Security Group Ltd | Financial services | 2025 |
| Black Pearl Executive Travel Ltd | Transport & logistics | 2022 |
| Black Rhino Integrated Limited | Administrative & support | 2025 |
| Black ROD Ltd | Professional & scientific | 2013 |
| Blackbird Ecological Ltd | Professional & scientific | 2026 |
| Blackchalk Ltd | Information & communication | 2024 |
| Blacker Watches Ltd | Manufacturing | 2023 |
| Blackfeather Dancewear Ltd | Wholesale & retail | 2026 |
| Blackmore Property Management Limited | Households | 2024 |
| Blackrock Estates Group Ltd | Real estate | 2026 |
| Blackshield Close Protection Ltd | Administrative & support | 2025 |
| Blackthorn Ventures Ltd | Hospitality | 2024 |
| Blackwood Accountants Limited | Professional & scientific | 2018 |
| Blackwood Architects Limited | Professional & scientific | 2006 |
| Blades Turf Care Ltd | Administrative & support | 2021 |
| Blair Property Holdings Limited | Real estate | 2017 |
| Blake Heating and Plumbing Ltd | Construction | 2021 |
| Blake Property Management (North) Limited | Administrative & support | 2007 |
| Blakes Financial Management Limited | Financial services | 2012 |
| Blakes Residential Limited | Real estate | 2020 |
| Blanchisseuse Limited | Administrative & support | 2021 |
| Blast Pressure Washing Ltd | Administrative & support | 2026 |
| Blasz Trans Limited | Transport & logistics | 2019 |
| Blenddius Limited | Hospitality | 2024 |
| Bliss Mill Ltd | Other services | 2016 |
| Bliss Software Solutions Ltd | Information & communication | 2013 |
| Blissful Residences Limited | Real estate | 2020 |
| Block & Butcher Ltd | Wholesale & retail | 2021 |
| Bloom Alternative Provision Ltd | Education | 2026 |
| Blooming Lotus UN Limited | Other services | 2024 |
| Blue Acorn Capital Ltd | Real estate | 2025 |
| Blue Group Properties Ltd | Real estate | 2024 |
| Blue Manta Media Limited | Professional & scientific | 2020 |
| Blue Mountain Logic Limited | Wholesale & retail | 2008 |
| Blue Rose Learning Limited | Professional & scientific | 2017 |
| Blue Rose Pictures Ltd | Information & communication | 2019 |
| Blue Sky Cooling Limited | Other services | 2014 |
| Blue World Counselling & Coaching Ltd | Other services | 2023 |
| Bluebell Court (Linslade) Management Company Limited | Real estate | 2018 |
| Blueboxx Creative Limited | Administrative & support | 2004 |
| Bluefox Accountancy Limited | Professional & scientific | 2025 |
| Blueleys Limited | Health & social care | 2009 |
| Blueprint Pixel Ltd | Financial services | 2026 |
| Bluesky V-Tech Ltd | Information & communication | 2023 |
| BLUESTONE3 Globe LLP | | 2008 |
| Blush Online Ltd | Other services | 2020 |
| BMC Concepts Ltd | Manufacturing | 2023 |
| BMG Labtech Limited | Wholesale & retail | 1996 |
| BMR Automotive Ltd | Wholesale & retail | 2024 |
| BMT Legals Limited | Professional & scientific | 2021 |
| BN Property Ltd | Real estate | 2019 |
| Bnacars Ltd | Transport & logistics | 2021 |
| BOB Banner Engineering Ltd | Professional & scientific | 2013 |
| BOB Care Services Limited | Health & social care | 2026 |
| BOB Networking Limited | Information & communication | 2024 |
| BOB Smith Contracting Limited | Construction | 2023 |
| Bobby Brown Garden Construction Limited | Administrative & support | 2024 |
| Boboc Group Limited | Construction | 2026 |
| Bockmer END Management Company Limited | Households | 2023 |
| Boden Furniture Ltd | Manufacturing | 2021 |
| Bodhi Couture Ltd | Wholesale & retail | 2026 |
| BODRUM46 Kebab Limited | Hospitality | 2019 |
| Bodygains Ltd | Wholesale & retail | 2024 |
| Bodygains Studio Ltd | Arts & recreation | 2026 |
| Bohra Consultancy Limited | Information & communication | 2010 |
| Boiling Point Ltd | Construction | 2025 |
| BOK BOK Limited | Administrative & support | 2021 |
| Bolders Care Ltd | Health & social care | 2015 |
| Bolero Drinks Ltd | Wholesale & retail | 2023 |
| Bond DNA Ltd | Professional & scientific | 2025 |
| Bonded Bottling Ltd | Manufacturing | 2021 |
| Bone Consultant (Kent) Limited | Health & social care | 2003 |
| Bone Holdings Limited | Administrative & support | 2022 |
| Bonhomie London Ltd | Wholesale & retail | 2022 |
| Bonsa Ltd | Wholesale & retail | 2024 |
| Bonsident Ltd | Health & social care | 2023 |
| Booby Trap Brewery Ltd | Manufacturing | 2008 |
| Booker Lane Management Company Limited | Households | 1985 |
| Bookkeeping Jemz Ltd | Professional & scientific | 2025 |
| BOR Holdings Limited | Financial services | 2025 |
| Borrow My Field Ltd | Other services | 2019 |
| Boscombe Forge Ltd | Households | 2017 |
| Boskee Ltd | Information & communication | 2017 |
| Boss Mums Circle Ltd | Administrative & support | 2025 |
| Both the Andrews Limited | Administrative & support | 2012 |
| Bounds Electrical Services Limited | Other services | 2007 |
| BOURNE2 Limited | Information & communication | 2017 |
| Boussofiane International HE Consultancy Limited | Education | 2019 |
| Bowdon Capital Ltd | Professional & scientific | 2014 |
| Bowen GAO Ltd | Professional & scientific | 2025 |
| Bowerbank Court Management Limited | Households | 1989 |
| Bowerbird Estate Agents Limited | Real estate | 2026 |
| Bowerman Building Services Limited | Construction | 2013 |