| Black Skin Directory Limited | London | 2018 |
| Black Spiral Design Ltd | Worthing | 2010 |
| Black Square Litho Ltd | Billericay | 2009 |
| Black Square Mode Ltd | Kingston Upon Thames | 2016 |
| Black Stag (London) Limited | Bexleyheath | 2019 |
| Black Star Assessments Limited | Poulton-Le-Fylde | 2020 |
| Black Star Strength Ltd | Truro | 2018 |
| Black Stock Barber Ltd | Sheffield | 2026 |
| Black Stone Financial Limited | Rainham | 2022 |
| Black Stone Industries Ltd | Belfast | 2016 |
| Black Stone Resources Ltd | Morley | 2019 |
| Black Stone Utility Limited | Rainham | 2022 |
| Black Stripe Consultancy Ltd | Chippenham | 2024 |
| Black Sultan Consultants Limited | Portsmouth | 2019 |
| Black Swan Leadership and Advisory Limited | London | 2024 |
| Black Swan One Ltd | Leicestershire | 2024 |
| Black Swan Physical Training Ltd | Halstead | 2024 |
| Black Swan Sauna Ltd | Teignmouth | 2026 |
| Black Swan Tattoo Studio Ltd | Sunderland | 2024 |
| Black Tapestry Tattoo Ltd | Worcester | 2021 |
| Black Tapestry Workshops Ltd | Worcester | 2024 |
| Black Tartan Limited | Aberdeen | 2024 |
| Black Taxi Hearse Hire Ltd | St. Albans | 2023 |
| Black Tiger Consultancy Ltd | London | 2021 |
| Black Tiger Global Limited | Harrow | 2010 |
| Black Tiger Limited | Hounslow | 2024 |
| Black Tories Ltd | Basildon | 2023 |
| Black Tulip Developments Limited | South Shields | 1993 |
| Black Tulip Limited | Royton | 2025 |
| Black Turtle Group Limited | Gravesend | 2023 |
| Black Vault Digital Ltd | Ashford | 2018 |
| Black Velvet Events Ltd. | Lichfield | 2015 |
| Black Velvet London Beauty Ltd | Haverhill | 2017 |
| Black Vulpine Group Ltd | London | 2025 |
| Black Water Tattoo Ltd | Kingston Upon Thames | 2019 |
| Black White Beauty Ltd | Glasgow | 2025 |
| Black Widow Studio Limited | Sutton-In-Ashfield | 2021 |
| Black Wolf Golf Limited | Church Broughton | 2023 |
| Black Woman Well Being CIC | London | 2023 |
| Black Women Business Awards Limited | Stevenage | 2018 |
| Black Women in Business UK CIC | London | 2020 |
| Black Women in Engineering CIC | London | 2023 |
| Black Women in Real Estate Ltd | London | 2023 |
| Black Zaitun Ltd | London | 2025 |
| Black&White Barber Ltd | Aberdeen | 2019 |
| BLACK5TONE UK Ltd | London | 2013 |
| Blackacre (Great Blakenham) 2 Limited | Colchester | 2022 |
| Blackadder 2025 Limited | Duns | 2025 |
| Blackball Tables Limited | Dunfermline | 2018 |
| Blackbeard Ltd | Hayes | 2013 |
| Blackberry Cottage Limited | Nottingham | 2011 |
| Blackbird Studio (Inverness) Limited | Inverness | 2025 |
| Blackbourns Limited | Boston | 2014 |
| Blackbox Barbers Limited | Berwick Upon Tweed | 2020 |
| Blackbox Quant Ltd | London | 2020 |
| Blackbox Solutions Holdings Ltd | London | 2017 |
| Blackbrae Parke Engineering (NI) Limited | Londonderry | 2019 |
| Blackbriar Services Limited | Barnet | 2009 |
| Blackbridge Asset Management Ltd | London | 2018 |
| Blackbull Media Group Ltd | London | 2022 |
| Blackburn and Wincobank Conservative Club Limited(The) | Sheffield | 1899 |
| Blackburn Cathedral Trust | Blackburn | 2009 |
| Blackburn Diocesan Board of Finance Limited | Blackburn | 1927 |
| Blackburn DIY Limited | Blackburn | 2014 |
| Blackburn Funeral Services Limited | Beverley | 2012 |
| Blackburn Hair Loss Clinic Ltd | Manchester | 2023 |
| Blackburn Incorporated Law Association(The) | Clitheroe | 1882 |
| Blackburn Phone Repairs Ltd | Blackburn | 2019 |
| Blackburn V.E. Limited | Nottingham | 1998 |
| Blackburn Vineyard Church | Blackburn | 2013 |
| Blackburn With Darwen Council for Voluntary Service | Blackburn | 1991 |
| Blackburn Ymca | Bolton | 2004 |
| Blackburn Youth Zone | Blackburn | 2009 |
| Blackbush Pet Services Ltd | Glasgow | 2026 |
| Blackbushe School of Flying 2012 Limited | Woking | 2012 |
| Blackbushe School of Flying Ltd | Woking | 2013 |
| Blackby Ltd | London | 2025 |
| Blackcat Plant & Groundworks Ltd | Barnsley | 2017 |
| Blackcrows Barbers Ltd | Bingley | 2023 |
| Blackcube International Ltd | London | 2025 |
| Blackcupid.Co.Uk Limited | Bedfordshire | 2000 |
| Blackdawn Limited | London | 2025 |
| Blackden Moorings Limited | Rochester | 2001 |
| Blackdiamond Contracting Ltd | Grimsby | 2013 |
| Blackdice Healthcare Limited | Devon | 2014 |
| Blackdivine Ltd | London | 2025 |
| Blackdog Haircutters Ltd | Falmouth | 2009 |
| Blackdown Aesthetics Ltd | Honiton | 2024 |
| Blackdown Rings Kennels & Cattery Limited | St. Neots | 2023 |
| Blackdown Storage Limited | Taunton | 2009 |
| Blackdown Trading Limited | Bridport | 2016 |
| Blackflower Ltd | Hounslow | 2025 |
| Blackfold Properties Limited | Redhill | 2025 |
| Blackgate Promotions Ltd | Blackpool | 2025 |
| Blackgold Data Services Ltd | Carlisle | 2008 |
| Blackgreaves Farmhouse Limited | Lea Marston | 2025 |
| Blackguild & Partners Limited | Redbridge | 2016 |
| Blackhair Media Limited | London | 2023 |
| Blackhall & Powis Ltd | Glasgow | 2017 |
| Blackhall Colliery Estates Limited | Salford | 2025 |