| Black and White Property Company Limited | Real estate | 2015 |
| Black Axle Ltd | Information & communication | 2025 |
| Black BEE Films Ltd | Information & communication | 2014 |
| Black Bluebell Care Services Limited | Health & social care | 2025 |
| Black Box Express Ltd | Transport & logistics | 2018 |
| Black Bricks BIO Ltd | Professional & scientific | 2023 |
| Black Bull Motors Ltd | Wholesale & retail | 2022 |
| Black Bulls Head Limited | Hospitality | 2011 |
| Black Butterfly (Nottingham) Limited | Real estate | 2022 |
| Black Cactus Ltd. | Professional & scientific | 2012 |
| Black Cat Accounting Ltd | Professional & scientific | 2011 |
| Black Cat Analytics Limited | Information & communication | 2012 |
| Black Cat Technology Ltd | Information & communication | 2011 |
| Black Chantry Productions Limited | Manufacturing | 2017 |
| Black Chapel Electrical Ltd | Construction | 2020 |
| Black Chapel Property Ltd | Real estate | 2018 |
| Black Curators Collective CIC | Arts & recreation | 2021 |
| Black Diamond (Holdings) Ltd | Professional & scientific | 2007 |
| Black Dove Consultancy Ltd | Administrative & support | 2020 |
| Black Dove Holdings Ltd | Professional & scientific | 2021 |
| Black Halo Games Ltd | Information & communication | 2011 |
| Black Hawk Productions Ltd | Information & communication | 2011 |
| Black Horse Utilities Ltd | Construction | 2025 |
| Black Lion Trading Company Limited | Hospitality | 2014 |
| Black Nectar Associates Ltd | Professional & scientific | 2025 |
| Black NOA Empire Ltd | Wholesale & retail | 2025 |
| Black Olive Marketing Limited | Professional & scientific | 2005 |
| Black Rock Resources LLP | | 2015 |
| Black Rose Photo & Video Production (Brpvp) CIC | Manufacturing | 2025 |
| Black Swan Marine Services Ltd | Manufacturing | 2022 |
| Black Telematics Box Ltd | Administrative & support | 2009 |
| Blackb Limited | Information & communication | 2024 |
| Blackbarrel Ltd | Wholesale & retail | 2014 |
| Blackberry Cottage Limited | Other services | 2011 |
| Blackbird Coffee Ltd | Hospitality | 2018 |
| Blackbourn Consulting Ltd | Professional & scientific | 2005 |
| Blackbrook Homes Limited | Real estate | 2025 |
| Blackburn V.E. Limited | Other services | 1998 |
| Blackcliffe Farm Ltd | Extraterritorial | 2016 |
| Blackcliffe Properties Ltd | Real estate | 2013 |
| Blackdown Foods Ltd | Hospitality | 2013 |
| Blackfen Limited | Real estate | 2023 |
| Blackford Bridge Properties Ltd | Households | 2020 |
| Blackhole Entertainment Ltd | Information & communication | 2025 |
| Blackie Ltd | Information & communication | 2025 |
| Blackjack FUN Casino Limited | Arts & recreation | 2012 |
| Blacklock Carpets Limited | Construction | 2002 |
| Blackmore Commercials Limited | Wholesale & retail | 2005 |
| Blackmouse Ltd | Information & communication | 2018 |
| Blackowl Productions Limited | Information & communication | 2002 |
| Blacksmiths Equipment UK Ltd | Wholesale & retail | 2022 |
| Blacksmiths Technology Ltd | Information & communication | 2019 |
| Blacksquare Ltd | Professional & scientific | 2024 |
| Blackstar Marketing Limited | Administrative & support | 2009 |
| Blackstaras Ltd | Wholesale & retail | 2025 |
| Blackstars Marketing Ltd | Administrative & support | 2025 |
| Blackstone Close Protection Ltd | Administrative & support | 2026 |
| Blackstone Hospitality Ltd | Hospitality | 2026 |
| Blackstone Legal Solutions Limited | Professional & scientific | 2024 |
| Blackstripe Ltd | Administrative & support | 2023 |
| Blackthorne Holdings Limited | Real estate | 2025 |
| Blackton Cross Limited | Real estate | 2021 |
| Blacktop Solutions Limited | Other services | 2021 |
| Blackwater Food Provision Limited | Wholesale & retail | 2009 |
| Blackwater Group Limited | Financial services | 1994 |
| Blackwell Bate Holdings Limited | Financial services | 2026 |
| Blackwell Mining and Mineral Engineering Limited | Arts & recreation | 1985 |
| Blackwell Property Company Limited | Real estate | 1980 |
| Blackwood Building Services Ltd | Construction | 2019 |
| Blackwood Property Developers Limited | Real estate | 2023 |
| Blade Ventures Limited | Manufacturing | 2021 |
| Bladerunners Commercial Cleaning Limited | Administrative & support | 2008 |
| Blades Restaurants Ltd | Hospitality | 2001 |
| Blagdens Kitchen & Bedroom Company Ltd | Construction | 2014 |
| Blake Accountants Limited | Professional & scientific | 2015 |
| Blake and Sons Electrical Ltd | Construction | 2021 |
| Blake Building Services Nottingham Ltd | Construction | 2021 |
| Blake Landa & Co Limited | Professional & scientific | 2009 |
| Blake Living Group Ltd | Real estate | 2026 |
| Blake Models Limited | Administrative & support | 2010 |
| Blake Recruitment Ltd | Administrative & support | 2022 |
| Blakebrooke Financial Advice Ltd | Financial services | 2020 |
| Blakey Brothers Limited | Construction | 2025 |
| Blanca Milani Limited | Professional & scientific | 2023 |
| Blanchard Property Limited | Real estate | 2021 |
| Blanche Consulting Ltd | Information & communication | 2019 |
| Blanchreno Ltd | Construction | 2024 |
| Bland Estates Limited(The) | Real estate | 1946 |
| Blank Space Creative Studios Ltd | Arts & recreation | 2025 |
| Blanks Medical Ltd | Health & social care | 2023 |
| Blanksy Ltd | Wholesale & retail | 2025 |
| Blckgld Limited | Manufacturing | 2020 |
| BLD Developments Limited | Construction | 2021 |
| Bleeding Poverty Ltd | Information & communication | 2022 |
| Blend Barbers Limited | Other services | 2008 |
| Blend Coffee House Ltd | Hospitality | 2017 |
| Blendworth Hills Management Limited | Households | 2023 |
| Blenheim 4C Limited | Real estate | 2013 |
| Blenkinsopp Castle Home Park Limited | Real estate | 2021 |
| Bless Care Services Ltd | Administrative & support | 2019 |