| Barkatuk Limited | Wholesale & retail | 2025 |
| Barker Carpentry Limited | Construction | 2017 |
| Barker Lettings Limited | Real estate | 2025 |
| Barn Cottage BN Limited | Administrative & support | 2023 |
| Barnaby Ollerhead Ltd | Education | 2025 |
| Base Dynamic Limited | Wholesale & retail | 2010 |
| Bathroom Value Limited | Wholesale & retail | 2025 |
| Bathrooms by Harpers Limited | Construction | 2016 |
| Bay Area Holding Ltd | Information & communication | 2016 |
| BB Care and Services Ltd | Other services | 2013 |
| BB Lettings Ltd | Real estate | 2024 |
| BB Security Ltd | Administrative & support | 2012 |
| BE Estates Investments Limited | Extraterritorial | 2014 |
| BE Your Own Finance Director Ltd | Professional & scientific | 2020 |
| Beatrix Properties Limited | Real estate | 2023 |
| Beautiful Rooms Northampton Limited | Real estate | 2016 |
| Beauty Secrets Milton Keynes Limited | Other services | 2018 |
| Beauty Trix Ltd | Other services | 2017 |
| Bedford MK Lettings Limited | Real estate | 2026 |
| Bedford Steelfixing Limited | Construction | 2017 |
| Beds & Bucks Properties Limited | Real estate | 1996 |
| Beechwood Court Residents Company Limited | Households | 1997 |
| Beeston Management Solutions Limited | Other services | 2015 |
| Bells Carpentry Ltd | Manufacturing | 2020 |
| Bemgatelaw Limited | Professional & scientific | 2025 |
| BEN Sterling Artist Ltd | Arts & recreation | 2022 |
| Berger Plumbing & Heating Limited | Construction | 2007 |
| Berkley Properties (Newport Pagnell) Limited | Real estate | 2020 |
| Bernard Crook Garden Services Limited | Agriculture & fishing | 1969 |
| Bespoke Creations Limited | Manufacturing | 2011 |
| Bespoke Vision Print Ltd | Construction | 2025 |
| BFS Consulting Ltd | Professional & scientific | 2024 |
| BG Management Services Ltd | Extraterritorial | 2022 |
| Bhandas Ltd | Extraterritorial | 2011 |
| Bhavna's Care Services Ltd | Health & social care | 2022 |
| BI Worldwide Holdings Limited | Professional & scientific | 2001 |
| BI Worldwide Limited | Administrative & support | 1979 |
| Big Bold Youth CIC | Arts & recreation | 2017 |
| Bill Griffiths Associates Limited | Real estate | 2009 |
| Biotzel Ltd | Professional & scientific | 2019 |
| Bishopsgate Kinsman Limited | Administrative & support | 2017 |
| BJF Consulting Limited | Information & communication | 2017 |
| BK Property Rentals Ltd | Real estate | 2021 |
| BKP Property Holdings Limited | Real estate | 2015 |
| Black & White Estate Agents LLP | | 2011 |
| Black Horse Lodge Management Company Ltd | Households | 2021 |
| Black Lake Construction Ltd | Construction | 2022 |
| Blast Group Limited | Financial services | 2024 |
| Bleak Down Holdings Ltd | Real estate | 2025 |
| BLP3 Investments Ltd | Real estate | 2017 |
| Blue Cat Mechanical Limited | Professional & scientific | 2021 |
| Blue Chess Recruitment Ltd | Health & social care | 2019 |
| Blue Morpho Consulting Ltd | Administrative & support | 2019 |
| Blue Morpho Holdings Ltd | Administrative & support | 2024 |
| Blue Mountain Property Solutions Ltd | Real estate | 2020 |
| Blue Teapot Training Limited | Administrative & support | 2017 |
| Bluehouse Music Consultancy Ltd | Other services | 2012 |
| Bluephase Electrical Ltd | Construction | 2026 |
| BM Biotech Ltd | Agriculture & fishing | 2019 |
| BMM Print Limited | Wholesale & retail | 2006 |
| Bmn-Investments (UK) Ltd | Real estate | 2012 |
| Bolt Events Limited | Administrative & support | 2024 |
| Boltozat Consulting Services Ltd | Professional & scientific | 2024 |
| Bond International Leasing Limited | Administrative & support | 2012 |
| Bonfire Creative Intelligence Limited | Professional & scientific | 2001 |
| Bonfire Retail Intelligence Limited | Extraterritorial | 2019 |
| Bonitas Consulting Limited | Professional & scientific | 2025 |
| Booths Window Cleaning Contractors Limited | Other services | 1988 |
| Box-Pro Limited | Professional & scientific | 2025 |
| Box-Pro Machinery Limited | Professional & scientific | 2001 |
| Boxpro Limited | Professional & scientific | 2025 |
| BR Conversions Ltd | Manufacturing | 2015 |
| Brackley House Management Company Limited | Households | 2008 |
| Brain UP Education Ltd | Administrative & support | 2018 |
| Brainfoods Neuro Ltd | Professional & scientific | 2026 |
| Brand Print (UK) Ltd | Manufacturing | 2009 |
| Brandshield Ltd | Professional & scientific | 1990 |
| Brave Stoat Limited | Professional & scientific | 2025 |
| Brawn Injury Rehabilitation Ltd | Health & social care | 2023 |
| Breastfeeding Hub Ltd. | Health & social care | 2018 |
| Brian West & SON Limited | Administrative & support | 2002 |
| Brick by Brick Movement Ltd | Wholesale & retail | 2025 |
| Brickmans Law Limited | Professional & scientific | 2022 |
| Bridgnorth Hospitality Ltd | Hospitality | 2024 |
| Brie Recruitment Ltd | Administrative & support | 2025 |
| Briggs Hulland Ltd | Construction | 2017 |
| BRIP0219 (Sutton) LLP | | 2019 |
| Britannia FM Supplies Ltd | Administrative & support | 2010 |
| Brite Sparks Limited | Extraterritorial | 1988 |
| Broadlands Estate Management LLP | | 2008 |
| Brocar Ltd | Financial services | 2021 |
| Brook END Consulting Limited | Professional & scientific | 2012 |
| Brooklands Barbers Ltd | Other services | 2023 |
| Brookson (5263D) Limited | Professional & scientific | 2007 |
| Brown, Heel and Tear Limited | Manufacturing | 2018 |
| BSG Consultancy Services Ltd | Information & communication | 2022 |
| BSS Property Investment Ltd | Real estate | 2015 |
| Bua's Kitchen Ltd | Hospitality | 2023 |
| Bucks BIZ Business Centres Ltd | Real estate | 2023 |
| Bucks Bizspace Ltd | Real estate | 2008 |