| Bags of Potential Limited | Professional & scientific | 2011 |
| Bahnstormer (Thames Valley) Limited | Extraterritorial | 2008 |
| Bahnstormer Motorrad Limited | Wholesale & retail | 2006 |
| Bakalov Ltd | Transport & logistics | 2016 |
| Balanced Business Advice Limited | Professional & scientific | 2020 |
| Ballantyne Associates Limited | Information & communication | 2008 |
| Ballycool Limited | Professional & scientific | 2020 |
| Bamber Bridge Cadrive Ltd | Administrative & support | 2024 |
| BAO BUN (Asia) Ltd | Financial services | 2022 |
| BAO BUN (Lisburn Road) Ltd | Hospitality | 2018 |
| BAO BUN Ltd | Hospitality | 2017 |
| Baran Dogan Ltd | Wholesale & retail | 2021 |
| Barford Investment Solutions Ltd | Real estate | 2023 |
| Barford Solutions Limited | Hospitality | 2003 |
| Bark 'N' Render Ltd | Hospitality | 2021 |
| Barkes Solutions Ltd | Professional & scientific | 2025 |
| Barnards Consulting Ltd | Professional & scientific | 2013 |
| Barnes MW Ltd | Professional & scientific | 2025 |
| Barometer Group Limited | Financial services | 2018 |
| Barometer Investments Limited | Financial services | 2014 |
| Barrow Studios Ltd | Information & communication | 2019 |
| Barton END House Management Limited | Households | 2002 |
| Basildon Cadrive Ltd | Administrative & support | 2024 |
| Basildon Hairdressing Limited | Education | 2012 |
| Basing Park Limited | Extraterritorial | 2009 |
| Basing Partners Limited | Real estate | 2000 |
| Basing Property Partners | | 2000 |
| Basingstoke Fireplace Centre Limited | Wholesale & retail | 2008 |
| Bassett Trust Limited | Financial services | 1931 |
| Bassy's Barn Community Interest Company | Agriculture & fishing | 2023 |
| Bath (T2) Hairdressing Limited | Other services | 2000 |
| Bath Cadrive Ltd | Administrative & support | 2024 |
| Batley Cadrive Ltd | Administrative & support | 2024 |
| Baudelaire Limited | Construction | 1976 |
| Baytree Business Services Limited | Professional & scientific | 2009 |
| Baywater Enterprise Limited | Other services | 2024 |
| Beechwood Heights (Beech) Management Company Limited | Households | 2010 |
| Beehive Gardening Services Limited | Administrative & support | 2020 |
| Beinn Eagagach Hydro LLP | | 2012 |
| Bellemoor Removals & Storage Ltd | Transport & logistics | 2014 |
| Bells Fencing Services Ltd | Other services | 2022 |
| Bellward Properties Ltd | Real estate | 2006 |
| Bennett's Office Cleaning Ltd | Administrative & support | 2019 |
| Bensons Yard Ltd | Real estate | 2025 |
| Bento Factory Company Limited | Hospitality | 2019 |
| Bentworth Hall Residents Association Limited | Water & waste | 1992 |
| Bentworth HR Ltd | Professional & scientific | 2014 |
| Bequip (UK) Limited | Administrative & support | 2008 |
| Bequip-Re Limited | Construction | 2007 |
| Bequipment Limited | Construction | 2008 |
| Berchem Limited | Professional & scientific | 2022 |
| Bespoke Construction Management Ltd | Construction | 2019 |
| Bespoke Tuning Limited | Wholesale & retail | 2019 |
| Bestower Home Ltd | Manufacturing | 2022 |
| Beswitched Limited | Information & communication | 2014 |
| Betafit PPE Ltd | Administrative & support | 2012 |
| Betpoint (Credit) Limited | Arts & recreation | 1994 |
| Bettertalkuk Ltd | Health & social care | 2025 |
| Beyond Engineering Ltd | Construction | 2017 |
| Bidscape Limited | Professional & scientific | 2017 |
| Big Dog Little Dog Limited | Arts & recreation | 2016 |
| Big Fish Little Fish Music Publishing Limited | Information & communication | 2014 |
| Big TEC Ltd | Wholesale & retail | 2013 |
| Billericay (T) Hairdressing Limited | Other services | 2003 |
| BIO Space Heritage & Sustainable Building Products Ltd | Wholesale & retail | 2024 |
| Birkenhead Cadrive Ltd | Administrative & support | 2024 |
| Birmingham (T2) Hairdressing Limited | Other services | 2022 |
| Birthglide Limited | Professional & scientific | 2019 |
| Bittraders Limited | Information & communication | 2000 |
| Black Executive Travel Services Ltd | Information & communication | 2023 |
| Black Hangar Films Limited | Information & communication | 2013 |
| Black Hangar Investment Limited | Information & communication | 2019 |
| Black Hangar Studios Ltd | Information & communication | 2009 |
| Black Hire Limited | Administrative & support | 2022 |
| Black Sets Ltd | Construction | 2022 |
| Blackheath (T) Hairdressing Limited | Other services | 2024 |
| Blackheath Salon Ltd | Other services | 2025 |
| Blacknest Hire Solutions Ltd | Administrative & support | 2026 |
| Blank Space Cleaning Limited | Administrative & support | 2021 |
| Blay Builders & Contractors Limited | Construction | 2003 |
| Blend IT Limited | Hospitality | 2019 |
| Blended Technical Training Services Ltd | Professional & scientific | 2013 |
| Bloom Management Ltd | Professional & scientific | 2024 |
| Bloomfield Health Holdings Limited | Financial services | 2021 |
| Bloomfield Health Limited | Health & social care | 2021 |
| Blue Bucket Productions Ltd | Information & communication | 2024 |
| Blue Eyed Panther Ltd | Other services | 2016 |
| Blue Pixel Limited | Information & communication | 2012 |
| Bluebell Cake House Limited | Hospitality | 2023 |
| Bluejay Music Group Ltd | Information & communication | 2015 |
| Bluejay Solutions Ltd | Wholesale & retail | 2024 |
| Bluewater (T) Hairdressing Limited | Other services | 2016 |
| Blush Beauty by Lauren Ltd | Other services | 2020 |
| Blygold Libya Limited | Administrative & support | 2009 |
| BM Property Insurance Services Limited | Financial services | 2008 |
| BMN Recruitment Ltd | Administrative & support | 2021 |
| BMN Spinningfields Ltd | Construction | 2018 |
| BOB and Co Ltd | Administrative & support | 2009 |
| Bodgit and Legit Roofing Limited | Construction | 2021 |
| Bodymagic Healthcare Limited | Health & social care | 2011 |