| Barakah Travel & Visa Service Ltd | Administrative & support | 2025 |
| Baranova Ltd | Professional & scientific | 2023 |
| Barge Close Management Company Limited | Professional & scientific | 2003 |
| Barge Court Management (NO. 2) Limited | Households | 2004 |
| Barnes Storage Ltd | Transport & logistics | 2024 |
| Barnett Davies Enterprises Limited | Other services | 2014 |
| Bascarau Ionel Ltd | Transport & logistics | 2015 |
| Basma's Plant Centre Ltd | Wholesale & retail | 2020 |
| Basto Transport Ltd | Transport & logistics | 2025 |
| Bates & Sons Properties Limited | Construction | 2024 |
| Batix Accommodation Limited | Real estate | 2025 |
| Battleboro Produce UK Ltd | Wholesale & retail | 2021 |
| BB Electrical Ltd | Construction | 2023 |
| BC Group Boston Ltd | Hospitality | 2020 |
| Bcsp V Europe, L.P. | | 2006 |
| Bcsp V-B Europe, L.P. | | 2007 |
| Bcsp VI Europe, L.P. | | 2008 |
| BDA Pizza Ltd | Hospitality | 2021 |
| BEA Cosmetics Ltd | Wholesale & retail | 2024 |
| BEA Properties Boston Ltd | Real estate | 2025 |
| Beammp Ltd | Information & communication | 2021 |
| Beateb Ltd | Wholesale & retail | 2026 |
| Beats & Shouting Limited | Wholesale & retail | 2023 |
| Beau Beauty and Skincare Specialist Ltd | Other services | 2022 |
| Beauts & Co 17 Ltd | Other services | 2023 |
| Beaver Radio Ltd | Information & communication | 2025 |
| Beba Group Ltd | Professional & scientific | 2025 |
| Bees N' Trees Ltd | Professional & scientific | 2016 |
| Beesons of Boston Limited | Construction | 1966 |
| Beira Alta Limited | Hospitality | 2026 |
| Bekazhan Limited | Wholesale & retail | 2025 |
| Bell Brothers Farms Limited | Agriculture & fishing | 2014 |
| Bellrox Research & Development Consultancy Limited | Wholesale & retail | 2019 |
| Benington Community Heritage Trust | Administrative & support | 2007 |
| Benington Conservatories Ltd | Manufacturing | 2026 |
| Benjamin O'Neill Flat Roofing Systems Ltd | Construction | 2022 |
| Benjonson Ltd | Construction | 2021 |
| Bennett Lighting Solutions Limited | Professional & scientific | 2025 |
| Benton Bros (Transport) Limited | Transport & logistics | 1958 |
| Berat Estates Ltd | Real estate | 2024 |
| Berati Ltd | Construction | 2019 |
| Beridge Lane Management Company Limited | Households | 2016 |
| Berkshire Green Limited | Professional & scientific | 2005 |
| Bernard French (Homes) Limited | Construction | 2004 |
| Berthoud Sprayers Limited | Manufacturing | 1986 |
| Bespoke Landscape Creations Ltd | Wholesale & retail | 2026 |
| BEST2CLEAN Limited | Administrative & support | 2018 |
| Beyond Beauty Boston Ltd | Other services | 2024 |
| Beyond the Veil CIC | Arts & recreation | 2026 |
| BG Wellness Ltd | Health & social care | 2024 |
| BGB Logistics Ltd | Transport & logistics | 2026 |
| BGC Hospitality Ltd | Hospitality | 2023 |
| Big Food Superstore Ltd | Wholesale & retail | 2025 |
| Big FOX Limited | Hospitality | 2025 |
| Big Sky Hideaway Ltd | Hospitality | 2021 |
| Bili Trans 2018 Ltd | Transport & logistics | 2025 |
| Billbump Investments Ltd | Real estate | 2021 |
| Billsinghproperties Ltd | Real estate | 2022 |
| BIM Plant Ltd | Construction | 2014 |
| Bioclean Solutions Ltd | Water & waste | 2025 |
| Biofly Ltd | Agriculture & fishing | 2024 |
| Bioveg Ltd | Manufacturing | 2018 |
| Birch Trees Birds Ltd | Wholesale & retail | 2025 |
| Birchwell (Developments) Ltd | Construction | 2020 |
| Birchwell (Northwood House) Ltd | Construction | 2024 |
| Birchwell (Property) Ltd | Real estate | 2018 |
| Birchwell (SA) Ltd | Hospitality | 2023 |
| Birsvic PVT Ltd | Health & social care | 2021 |
| Bismillah Foods Boston Ltd | Wholesale & retail | 2025 |
| Bizads Bureau Ltd. | Information & communication | 2013 |
| BK Consulting Engineers Limited | Construction | 2026 |
| Black Bravo Limited | Wholesale & retail | 2025 |
| Black Brick ADK Ltd | Real estate | 2024 |
| Black Cat Hospitality Ltd | Hospitality | 2021 |
| Black Mosaic Limited | Other services | 2016 |
| Black Sky & Sun Limited | Transport & logistics | 2019 |
| Black Sluice Conference and Consultancy Limited | Information & communication | 2014 |
| Blackbird Lincs Ltd | Administrative & support | 2017 |
| Blackbourns Limited | Other services | 2014 |
| Blackfriars Club Limited | Hospitality | 1984 |
| Blind Socials Ltd | Professional & scientific | 2023 |
| Blindco Ltd | Manufacturing | 2013 |
| Blockspec Property Management Limited | Real estate | 2025 |
| Blond Hospitality Limited | Hospitality | 2018 |
| Bloodsight Health Ltd | Information & communication | 2025 |
| BLU Maintenance & Logistics Limited | Households | 2025 |
| Blue Bell & Friends Ltd | Hospitality | 2022 |
| Blue Edge Accountants Limited | Professional & scientific | 2024 |
| Blue Horizon Training Limited | Education | 2014 |
| Blue Spray Painters Ltd | Construction | 2025 |
| Blue Star Shipping Ltd | Professional & scientific | 2016 |
| Blue Waters Limited | Financial services | 2009 |
| Bluebell Restorations Ltd | Other services | 2023 |
| Blvckrose ENT Ltd | Wholesale & retail | 2025 |
| Blythe Cottages Norfolk Ltd | Hospitality | 2020 |
| Blythe Properties Limited | Real estate | 2007 |
| BMG Property Providers Ltd | Real estate | 2024 |
| Bmlc Holdings Limited | Arts & recreation | 2025 |
| Boann Aesthetics Limited | Administrative & support | 2023 |
| BOB Wildings Limited | Wholesale & retail | 1998 |