| BL Joshi Holdings Limited | Wembley | 2002 |
| BL Optical Holdings Ltd | Walsall | 2026 |
| BL Portman Square Limited | London | 2020 |
| BL Thanet Limited | London | 2022 |
| BL West END Offices 2 Limited | London | 2020 |
| BL West END Offices 3 Limited | London | 2020 |
| BL West END Offices Limited | London | 2020 |
| Bl(I)Ss Helston Limited | Helston | 2015 |
| BLA Holdings Limited | Newton Aycliffe | 2021 |
| Blaaiz Innovations Technology Ltd | Borough | 2023 |
| Blabla Holdings Ltd | Bury St. Edmunds | 2017 |
| Blaby Group Limited | Wigston | 2023 |
| Blac Square Limited | Telford | 2025 |
| Black & Gold Financial Services Limited | Manchester | 2017 |
| Black & White Financial Planning Ltd | Dover | 2012 |
| Black & White Financial Solutions Ltd | Leeds | 2012 |
| Black & White Outsourcing Ltd | Kings Langley | 2005 |
| Black & White Stripes Holdings Limited | Eastbourne | 2021 |
| Black Ace Limited | Edinburgh | 2014 |
| Black and Callow Holdings Limited | London | 2017 |
| Black and White Asset Finance Limited | Teignmouth | 2016 |
| Black and White Group Holdings Ltd | Stevenage | 2025 |
| Black and White Investments | Darlington | 2014 |
| Black ARK Capital Ltd | London | 2022 |
| Black Arrow Group Limited | Brentford | 1959 |
| Black Arrow Investments Limited | Holywood | 2014 |
| Black Arrow Yachting Limited | London | 2023 |
| Black Atom Holdings Limited | Aberdeen | 2022 |
| Black Barn Investments Limited | Faversham | 2025 |
| Black Bay Group Limited | London | 2021 |
| Black Bean Café Limited | London | 2022 |
| Black Bear (Holdings) Limited | Corsham | 2011 |
| Black Bear Assets Limited | Northwood | 2023 |
| Black Bear PUB Group Limited | Southmoor | 2024 |
| Black Beatles Ltd | Wolverhampton | 2025 |
| Black Blossom Ltd | Sheffield | 2021 |
| Black Book & Co. Ltd | Sutton Coldfield | 2024 |
| Black Box Ventures Ltd | Manchester | 2025 |
| Black Brick Investing Ltd | Hounslow | 2023 |
| Black Bull Banteng Hitam Ban's Blockchain Ltd | London | 2025 |
| Black Bull Capital Limited | Stratford-Upon-Avon | 2024 |
| Black Bull Capital Partners Ltd | Stratford-Upon-Avon | 2022 |
| Black Business Founders CIC | Liverpool | 2025 |
| Black Capital Group Ltd | Liverpool | 2024 |
| Black Castle Capital Partners Limited | London | 2017 |
| Black Cat Associates (London) Limited | Harrow | 2019 |
| Black Cat Associates Limited | Harrow | 2023 |
| Black Cat GRP Limited | Chatham | 2023 |
| Black Cat Holdings Ltd | Watford | 2023 |
| Black Cat Partnership Limited | Leicester | 1993 |
| Black Cat Strategic Projects Ltd | Dagenham | 2026 |
| Black Chords Limited | London | 2022 |
| Black Country Engineering Limited | Oldbury | 2020 |
| Black Country Holdings and Investments Ltd | Dudley | 2025 |
| Black Country Mortgages Ltd | Wolverhampton | 2025 |
| Black COW Agencies Ltd | Banbridge | 2025 |
| Black COW Holdings Limited | Banbridge | 2026 |
| Black Cow-Jjk (UK) Buyer Co Limited | London | 2024 |
| Black Crow Resources Ltd | London | 2025 |
| Black Crown Capital Limited | Kidderminster | 2018 |
| Black Crown Group Limited | Birmingham | 2023 |
| Black Cube Enterprise Ltd | Birmingham | 2025 |
| Black Cube Ltd | Sandbach | 2024 |
| Black DHU Financial Ltd. | Aberdeen | 2007 |
| Black Diamond Asset Management Limited | Renfrewshire | 2019 |
| Black Diamond Brokers Ltd | Egham | 2020 |
| Black Diamond Group Limited | Sheffield | 2022 |
| Black Diamond Holding Group Limited | London | 2023 |
| Black Dock Ltd | Romsey | 2024 |
| Black Dog Capital Limited | London | 2016 |
| Black Dog Financial Services Ltd. | Fochabers | 2004 |
| Black Dog Genus Ltd | Poole | 2024 |
| Black Dove Systems Ltd | London | 2025 |
| Black Dragon Holdings Ltd | Haverfordwest | 2023 |
| Black Drop Security Limited | Bury St. Edmunds | 2025 |
| Black Eagle Group Limited | Solihull | 2021 |
| Black EYE Collective Ltd | Birmingham | 2019 |
| Black EYE Holdings Ltd | Sheffield | 2020 |
| Black EYE Ventures Ltd | Birmingham | 2025 |
| Black Family Limited | Wetherby | 2025 |
| Black FIN Investments (UK) Limited | Ramsgate | 2016 |
| Black Financial Services Limited | Gravesend | 2014 |
| Black Flag Solutions Ltd | Cannock | 2022 |
| Black Flock Holding | Crowton | 2025 |
| Black Folder Consulting Limited | Luton | 2009 |
| Black Forest Holdings Ltd | Kings Lynn | 2025 |
| Black FOX Advisory Ltd | London | 2019 |
| Black FOX Finance Ltd | Bury St. Edmunds | 2020 |
| Black FOX Financial Limited | Calne | 2016 |
| Black FOX Group Ltd | London | 2019 |
| Black FOX Holdings Ltd | Cardiff | 2025 |
| Black Friars Lane Investments Limited | London | 2026 |
| Black Global Investments Limited | London | 2018 |
| Black Goat Investments Ltd | Dudley | 2025 |
| Black GOO (UK) Limited | Hitchin | 2022 |
| Black Graphite Architects Ltd | Esher | 2025 |
| Black Ground Holdings Limited | London | 2020 |
| Black Hall Associates Limited | Taunton | 1994 |
| Black Hammer Capital Limited | London | 2006 |
| Black HAT Properties Ltd | Canvey Island | 2008 |