| Big Red Rigging and Services Ltd | Construction | 2025 |
| Bigchef Kebab Limited | Hospitality | 2024 |
| Bigkart Limited | Manufacturing | 2024 |
| Bigwillow Limited | Information & communication | 2025 |
| Billings Method England Community Interest Company | Education | 2024 |
| Billionairr Limited | Other services | 2022 |
| Bimglobal Services Limited | Health & social care | 2025 |
| Bingley Developments Limited | Construction | 2007 |
| Bingol Kebab & Pizza Ltd | Hospitality | 2024 |
| Bingol Kebab (Stevenage) Ltd | Hospitality | 2018 |
| Bio-Mimetic Chromatography Ltd | Professional & scientific | 2017 |
| BIOA3 Ltd | Professional & scientific | 2025 |
| BIOCLEAN247 Ltd | Administrative & support | 2025 |
| Biores Ltd | Professional & scientific | 2025 |
| Biotech Enthusiast Ltd | Professional & scientific | 2023 |
| Biowizard Ltd. | Manufacturing | 2015 |
| Bipsol Consulting Ltd | Information & communication | 2020 |
| Birchwood Healthcare Ltd | Information & communication | 2018 |
| Birchwood Home Improvements Limited | Other services | 2009 |
| Bish Productions Ltd | Information & communication | 2015 |
| Bishops Court (Luton) Limited | Households | 1994 |
| Bistro Group Limited | Hospitality | 2023 |
| Bitflips Ltd | Information & communication | 2025 |
| Biwas Limited | Health & social care | 2020 |
| Bizarrebeautiful Limited | Professional & scientific | 1999 |
| BJC Fire and Security Limited | Administrative & support | 1991 |
| BJC Property Maintenance Limited | Construction | 2016 |
| BKM Building Solutions Ltd | Construction | 2025 |
| BKM Scaffolding Ltd | Construction | 2016 |
| BL Architecture & Design Limited | Professional & scientific | 2019 |
| BL4NCS Ltd | Wholesale & retail | 2023 |
| Black & White Fire & Security Limited | Wholesale & retail | 2018 |
| Black & White Fire Safety Ltd | Wholesale & retail | 2006 |
| Black and White Group Holdings Ltd | Financial services | 2025 |
| Black Women Business Awards Limited | Other services | 2018 |
| Blackberry Way Management (NO.1) Limited | Households | 1990 |
| Blackbox AI Ltd | Information & communication | 2025 |
| Blackdown Capital Limited | Real estate | 2021 |
| Blackrobin Contractors Ltd | Construction | 2019 |
| Blackwood Property Renovations Ltd | Real estate | 2021 |
| Blade Sets Ltd | Administrative & support | 2014 |
| Blajo Limited | Information & communication | 2022 |
| Blakes Grips Ltd | Other services | 2016 |
| Blakout Productions Ltd | Information & communication | 2024 |
| Blank Page Pictures Ltd | Information & communication | 2020 |
| Blenniella Limited | Health & social care | 2023 |
| Blest Nightclub Limited | Hospitality | 2018 |
| Blitz Hospitality Ltd | Hospitality | 2017 |
| Blizzard Hospitality Ltd | Hospitality | 2019 |
| Blokeys Limited | Other services | 2024 |
| Blooms Auction Ltd | Administrative & support | 2026 |
| Blooq Technology Limited | Information & communication | 2020 |
| Blossom Belle Holdings Ltd | Real estate | 2024 |
| Blue Cat in London Ltd | Hospitality | 2021 |
| Blue Dreamer Productions Limited | Information & communication | 2017 |
| Blue Flame PH Ltd | Construction | 2025 |
| Blue Hilltop Ltd | Real estate | 2021 |
| Blue River Innovations Ltd | Manufacturing | 2015 |
| Blue Sector Ltd | Water & waste | 2025 |
| Bluebell and JOE Ltd | Arts & recreation | 2019 |
| Bluebird Technology Consulting Limited | Information & communication | 2016 |
| Bluekey Asset Management Ltd | Real estate | 2023 |
| Bluekey Ventures Ltd | Wholesale & retail | 2025 |
| Blueprint Civil Engineering Ltd | Professional & scientific | 2025 |
| Bluestone Trades Ltd | Real estate | 2020 |
| Blueview Homes Limited | Real estate | 2023 |
| BM Care Consultancy Limited | Public administration | 2025 |
| BM Pearson Ltd | Health & social care | 2006 |
| BMD Solution Ltd | Construction | 2022 |
| BMI Logistics Limited | Transport & logistics | 2025 |
| BMS Intelligent Services Limited | Construction | 2013 |
| Boardwalk Homes Ltd | Real estate | 2017 |
| Boardwalk Trading Limited | Wholesale & retail | 2019 |
| BOB Ferguson Communications Limited | Administrative & support | 2012 |
| Bobby West Scenic Art Ltd | Arts & recreation | 2020 |
| Bobrova Ltd | Real estate | 2021 |
| Bobs Upvc Limited | Water & waste | 2013 |
| Body Tech South Ltd | Arts & recreation | 2024 |
| Body Transformations Limited | Other services | 2003 |
| BOG Brew Beers Limited | Manufacturing | 2018 |
| Bogatu Ltd | Transport & logistics | 2019 |
| Boheme Social Ltd | Professional & scientific | 2023 |
| Bohemiaroasts Ltd | Wholesale & retail | 2019 |
| Boiler and Heating Repair Ltd | Construction | 2016 |
| Bokke Investments Limited | Real estate | 2020 |
| Bolad Healthcare Ltd | Health & social care | 2017 |
| Bold Moves Family Services Limited | Health & social care | 2025 |
| Bold Moves Family Time Community Interest Company | Health & social care | 2025 |
| Boleyn Consultancy Ltd | Construction | 2023 |
| Boltop Autos Limited | Wholesale & retail | 2025 |
| Bona Mensura Limited | Professional & scientific | 2024 |
| Bonano Ltd | Construction | 2025 |
| Bonco Leasing Limited | Wholesale & retail | 2017 |
| Bonita Eloise Limited | Wholesale & retail | 2025 |
| Bonsai AZ Management Limited | Education | 2013 |
| Born Editions Limited | Wholesale & retail | 2025 |
| Borsawork Ltd | Construction | 2021 |
| Boschi Works Ltd | Information & communication | 2017 |
| Botanic Law Limited | Other services | 2019 |
| Bothwell Investments Ltd | Real estate | 2021 |