| Black Lion 2025 Limited | London | 2025 |
| Black Lotus Coaching Ltd | London | 2024 |
| Black Lyon Blood Limited | London | 2024 |
| Black Machine Limited | London | 1993 |
| Black Magix Limited | Manchester | 2025 |
| Black Mango Art Ltd | Chester | 2017 |
| Black Market London Limited | Sittingbourne | 2009 |
| Black Mile Limited | London | 2017 |
| Black Mind Ltd | London | 2022 |
| Black MOG Ltd | London | 2017 |
| Black Moon INK Ltd | Glasgow | 2022 |
| Black Mountain Activities Limited | Brecon | 2003 |
| Black Mountain Racing Ltd | Llandeilo | 2026 |
| Black Mountains Cycle Centre Ltd | Crickhowell | 2014 |
| Black Mountains Gliding Club | Brecon | 1996 |
| Black Noise Limited | London | 2021 |
| Black One Sugar Ltd | Wirral | 2018 |
| Black Orchid Empire Limited | London | 2020 |
| Black Palfrey Motor Club of Kent Limited | West Malling | 1982 |
| Black Panther Dons Community Football Club and Academy Limited | Windsor | 2022 |
| Black Park Community Centre Ltd | Wrexham | 2014 |
| Black Pearl Divers Ltd | London | 2025 |
| Black Pearl Productions Limited | Stratford Upon Avon | 2021 |
| Black Pearl Tattoo Parlour Limited | Donnington | 2014 |
| Black Pearl Tour Production Ltd | Manchester | 2021 |
| Black Planet Limited | Saffron Walden | 2021 |
| Black Pudding Limited | London | 1976 |
| Black RAT Productions Ltd | Pwll Gwaun | 2011 |
| Black RAT Scenery Limited | Esher | 2015 |
| Black Rock Dive Centre UK Limited | Carlisle | 2014 |
| Black Rock Outdoors Limited | Weston-Super-Mare | 2008 |
| Black Sabbath Records Limited | London | 1993 |
| Black Salamander Limited | London | 2019 |
| Black Schnauzer Productions Limited | Leyland | 2026 |
| Black Science Labs Limited | Wimborne | 2017 |
| Black Sheep Comedy Limited | Broadstairs | 2003 |
| Black Sheep Tattoo Studio Ltd | Buckley | 2024 |
| Black Ship Communications Limited | Lewes | 2012 |
| Black Shuck Festival CIC | Bungay | 2024 |
| Black Skull Productions Limited | Halstead | 2013 |
| Black Skull Studio Limited | Halstead | 2020 |
| Black Skull Talent Limited | Halstead | 2024 |
| Black Spaniel Limited | London | 2016 |
| Black Sparrow Limited | London | 2010 |
| Black Spectre Entertainment Ltd | Croydon | 2023 |
| Black Squirrel Limited | London | 2016 |
| Black Stag Community Fitness Ltd | Glasgow | 2019 |
| Black Stag Ltd | Stroud | 2020 |
| Black Star Riders Limited | Abingdon | 2019 |
| Black Swan Arts Ltd | Frome | 1985 |
| Black Swan Dance Studios Ltd | Grimsby | 2020 |
| Black Swan Festivals Limited | Sutton | 2018 |
| Black Swan Tennis Ltd | London | 2022 |
| Black TEE Club Ltd | Maidstone | 2026 |
| Black Thunder Boxing Ltd | Belfast | 2026 |
| Black TIE Boxing Ltd | Northampton | 2025 |
| Black to the Trails Limited | London | 2025 |
| Black Toast Ltd | London | 2024 |
| Black Tongue Events Ltd | Scunthorpe | 2025 |
| Black Tower Projects Ltd | London | 2018 |
| Black Train Music C.I.C. | Solihull | 2018 |
| Black Twist Films Ltd | London | 2020 |
| Black Velvet Entertainment Ltd | Harefield | 2018 |
| Black WAX Music Ltd | Harlow | 2018 |
| Black Welsh Music Awards CIC | Swansea | 2025 |
| Black Widow Martial Arts Ltd | Birmingham | 2025 |
| Black Wire Music Limited | Abingdon | 2013 |
| Black Women on Wheels CIC | London | 2022 |
| Black+Cheneviere Ltd | St. Neots | 2025 |
| Black, Asian & Mixed Heritage Referee Support Group Ltd | London | 2023 |
| Blackajack Productions Ltd | Birmingham | 2014 |
| Blackamoor Films Ltd | Borehamwood | 2022 |
| Blackat Fitness Clubs Ltd | Birmingham | 2017 |
| Blackballed Ltd | Petworth | 2021 |
| Blackbeard Academy Group Limited | Manchester | 2026 |
| Blackbeard Community Projects CIC | Slough | 2020 |
| Blackberry Fair Community Interest Company | Whitchurch | 2009 |
| Blackberry Fields Limited | Hassocks | 2009 |
| Blackbird Creative Arts Ltd | Darlington | 2019 |
| Blackbird Creative Studio Ltd | Sheffield | 2023 |
| Blackbird Film Productions Limited | London | 2017 |
| Blackbird Films Limited | Buckingham | 2017 |
| Blackbird Pictures Ltd | London | 2010 |
| Blackbird Touring Ltd | Wigan | 2025 |
| Blackbody Limited | Lincoln | 2009 |
| Blackbow Creative Ltd | Lincoln | 2018 |
| Blackbox Productions Group Limited | London | 2018 |
| Blackbox Theatre Ltd | Glasgow | 2024 |
| Blackbrook Country Sports Limited | Tamworth | 2013 |
| Blackburn & Hallum Ltd | London | 2014 |
| Blackburn Academy of Martial Arts CIC | Burnley | 2016 |
| Blackburn Cricket Academy Ltd | Blackburn | 2025 |
| Blackburn Empire Theatre Ltd | Blackburn | 1979 |
| Blackburn Festival of Light CIC | Blackburn | 2017 |
| Blackburn Hawks Academy Limited | Preston | 2019 |
| Blackburn International (UK) Limited | Camberley | 2000 |
| Blackburn Martial Arts & Kickboxing Club Ltd | Darwen | 2010 |
| Blackburn OFC Limited | Gloucester | 2023 |
| Blackburn Rovers Women Football Club Limited | Blackburn | 2019 |
| Blackburn Snooker Ltd | Blackburn | 2023 |