| Black Rock Dental Limited | Kilgetty | 2014 |
| Black Rock Trading Company Ltd | Ponteland | 2011 |
| Black Rose Beauty Limited | London | 2023 |
| Black Sand Medical Limited | Wilmslow | 2024 |
| Black Shakira Limited | Leigh | 2023 |
| Black Sheep Wellbeing Ltd | Pontefract | 2025 |
| Black Stone Medical Limited | Manchester | 2022 |
| Black Swan Care Ltd | Teignmouth | 2019 |
| Black Swan Dental Spa Limited | Crewkerne | 2012 |
| Black Swan Homecare Limited | Norwich | 2025 |
| Black Swan International Limited | Norwich | 1991 |
| Black Swan Osteopathic Clinics Ltd | St. Neots | 2011 |
| Black Therapy Matters CIC | London | 2019 |
| Black Tiger Distribution Ltd | Manchester | 2019 |
| Black Trans Foundation C.I.C. | St. Albans | 2021 |
| Black Unity Alliance Ltd | London | 2025 |
| Black Voices Matter CIC | Longford | 2025 |
| Black* Artists on the Move CIC | Taunton | 2024 |
| Blackabey's Happy Skin Company Limited | Leeds | 2024 |
| Blackadder Corporation 3 Limited | Leamington Spa | 2013 |
| Blackadder Corporation Contracting Limited | Leamington Spa | 2020 |
| Blackadder Corporation II Limited | Leamington Spa | 2017 |
| Blackadder Corporation Limited | Leamington Spa | 2011 |
| Blackbear Healthcare Limited | Chatham | 2021 |
| Blackbelt Chiroh Ltd | Borehamwood | 2025 |
| Blackberry Clinic Limited | London | 2015 |
| Blackberry Hill Limited | Borehamwood | 2004 |
| Blackberry Homecare Ltd | Peterborough | 2015 |
| Blackbird Leys Neighbourhood Support Scheme Limited | Oxfordshire | 1991 |
| Blackbird Medical Consulting Limited | Edale | 2025 |
| Blackbird Practice Limited | Leicester | 2022 |
| Blackbird Psychology Ltd | Daventry | 2026 |
| Blackbirds Consultancy Limited | Wokingham | 2022 |
| Blackbrook House Care Limited | Fareham | 2009 |
| Blackbrook Pathology Limited | Yelverton | 2026 |
| Blackburn & District Supported Housing Limited | Blackburn | 1997 |
| Blackburn & PAI Limited | Romsey | 2003 |
| Blackburn Eyecare Limited | Blackburn | 2013 |
| Blackburn Healthcare Ltd | Manchester | 2009 |
| Blackburn Practice Limited | Rossendale | 2011 |
| Blackburn Smilecare Limited | Preston | 2016 |
| Blackburn West Medical Services Limited | Merseyside | 2016 |
| Blackburn With Darwen Carers Service Ltd | Blackburn | 2006 |
| Blackburn With Darwen Healthy Living | Lancashire | 2007 |
| Blackdown Anaesthesia Ltd | Cullompton | 2024 |
| Blackdown Hearing Ltd | Taunton | 2020 |
| Blackdown Psychology Ltd | Honiton | 2003 |
| Blackdrop Ltd | Bradford | 2021 |
| Blackdynamite Limited | London | 2018 |
| Blacker Excellence Ltd | London | 2025 |
| Blackexotics Ltd | Harrogate | 2016 |
| Blackfaulds Care at Home Ltd | Glasgow | 2021 |
| Blackfaulds House Nursing Home Limited | Glasgow | 1997 |
| Blackfen Osteopathic Clinics Limited | Maidstone | 2003 |
| Blackfen Private GP Ltd | Sidcup | 2025 |
| Blackfriars Dental Limited | Slough | 2021 |
| Blackfriars Medical Practice Ltd. | London | 2019 |
| Blackham Nanny Services Ltd | London | 2023 |
| Blackheath Aesthetics Ltd | London | 2020 |
| Blackheath and LEE Holding Ltd | London | 2026 |
| Blackheath Care Limited | Egham | 2016 |
| Blackheath Eyecare Limited | Croydon | 2012 |
| Blackheath Osteopathy Limited | London | 2016 |
| Blackheath Psychotherapy Limited | Dartmouth | 2024 |
| Blackheath Psychotherapy Practice Ltd | London | 2021 |
| Blackheath Yoga Ltd | London | 2018 |
| Blackhills Clinic Limited | Edinburgh | 2006 |
| Blackhurst Care Home Limited | Shropshire | 2006 |
| Blackie Solutions Limited | London | 2016 |
| Blackisle Medical Ltd | Inverness | 2022 |
| Blackledge and Leslie Limited | Kidderminster | 2013 |
| Blackmer Advisory Ltd | London | 2026 |
| Blackmoor Croft Health Care Limited | Sheffield | 2019 |
| Blackmoor Health Care Limited | Bordon | 2014 |
| Blackmore Chiropractic Ltd. | Glasgow | 2000 |
| Blackpearl Services Limited | Ruislip, | 2025 |
| Blackpool & Wyre HI Limited | Thornton-Cleveleys | 2013 |
| Blackpool Carers Centre Limited | Blackpool | 2005 |
| Blackpool Physiotherapy Centre Limited | Lancashire | 2004 |
| Blackpool Smile Centre Ltd | Widnes | 2026 |
| Blackpool South Central Ltd | Preston | 2024 |
| Blackrain Medical Limited | Chester | 2017 |
| Blackridge Stone Ltd | Yarm | 2025 |
| Blackroche Ltd | Rugby | 2014 |
| Blackrock Imaging Ltd | Newcastle Upon Tyne | 2022 |
| Blackrod House Limited | Bolton | 2015 |
| Blackrose Sonu Ltd | Crewe | 2026 |
| Blackshots Osteopathic Centre Limited | Grays | 2013 |
| Blackstaff Diagnostics Ltd | Belfast | 2019 |
| Blackstar Health & Material Science Ltd | Ilford | 2009 |
| Blackstone Care Homes Ltd | Barnet | 2026 |
| Blackstone Care Services Ltd | Doncaster | 2019 |
| Blackstone Support and Services Limited | Birmingham | 2023 |
| Blackstone Therapies Ltd | Burton-On-Trent | 2025 |
| Blackstone Wells Limited | Standish | 2018 |
| BLACKTALON21 Ltd | Portsmouth | 2025 |
| Blackthorn and Brook Ltd | Haywards Heath | 2022 |
| Blackthorn Solutions CIC | Chatham | 2024 |
| Blackwater Dental Surgery & Implant Centre Ltd | Camberley | 2023 |
| Blackwater EAR Care Ltd | Maldon | 2024 |