| Black TAP Investments Ltd | Rochdale | 2024 |
| Black Telos Capital Limited | Swindon | 2024 |
| Black Thistle FIC Limited | Dalgety Bay | 2026 |
| Black Tier Capital Ltd | Redhill | 2025 |
| Black Trader Limited | Ruislip, London | 2024 |
| Black Trident Holdings Limited | Chatham | 2014 |
| Black Tusk Investments Limited | Newcastle Upon Tyne | 2022 |
| Black Twelve Limited | Oswestry | 2026 |
| Black Umbrella Holdings Ltd | York | 2020 |
| Black Unicorn Group Ltd | London | 2025 |
| Black Vault Partners Ltd | Mirfield | 2025 |
| Black Venture Capital Ltd | Ipswich | 2018 |
| Black Volcano Limited | Harrow | 2017 |
| Black Volta Limited | London | 2019 |
| Black Volta Ventures (UK) Limited | London | 2019 |
| Black Water Capital Management Limited | Brough | 2016 |
| Black Widow Holdings Ltd | Royston | 2026 |
| Black Widows (Sussex) Ltd | Hailsham | 2020 |
| Black Widows Bikers Ltd | Hailsham | 2020 |
| Black&White Enterprises Limited | Bexleyheath | 2026 |
| Black's Test Centre Holdings Limited | Montrose | 2019 |
| Black-Lyon Trading Limited | Kettering | 2024 |
| Black-Scholes Limited | London | 2023 |
| Blackacre Holdco Limited | Preston | 2025 |
| Blackacre Newco 1 Limited | Skelmersdale | 2025 |
| Blackacre Newco 2 Limited | Ormskirk | 2025 |
| Blackarc Group Ltd | Ashington | 2024 |
| Blackb Financial Services Limited | Luton | 2017 |
| Blackbarn Advisory Ltd | Brentwood | 2026 |
| Blackbear Finance Limited | Swansea | 2025 |
| Blackbear Financial Group Ltd | Ellesmere Port | 2017 |
| Blackbeard Holdings Limited | Poole | 2021 |
| Blackberries Holdings Limited | Wisbech | 2022 |
| Blackberry Clinic Group Limited | London | 2015 |
| Blackberry Estate Holdings Ltd | Wetherby | 2026 |
| Blackberry Finance Solutions Limited | Luton | 2007 |
| Blackbird Capital Investments Limited | Solihull | 2021 |
| Blackbird Concepts Ltd | Belfast | 2022 |
| Blackbird Holdings (SW) Ltd | Launceston | 2023 |
| Blackbird Innovation Group Ltd | Wakefield | 2021 |
| Blackbird Property Holdings Ltd | Leicester | 2026 |
| Blackbird TMT Limited | Harrow | 2013 |
| Blackbird Ventures Ltd | Dunblane | 2025 |
| Blackbird Yard NOM1 Limited | Victoria Street | 2023 |
| Blackbird Yard NOM2 Limited | Altrincham | 2023 |
| Blackborough Holdings Ltd | Reigate | 2026 |
| Blackbotsch Invest Ltd | London | 2021 |
| Blackbox Holdings Limited | Harrow | 2019 |
| Blackbox Investments and Property Ltd | Kettering | 2019 |
| Blackbriar (Holdings) Ltd | Halifax | 2024 |
| Blackbridge Capital Ltd | St. Albans | 2023 |
| Blackbridge Group Holdings Limited | Kettering | 2022 |
| Blackbridge Investment Swiss Ltd | London | 2025 |
| Blackbrook Asset Management Ltd | London | 2014 |
| Blackbrook Capital (Europe) Limited | London | 2019 |
| Blackbrook Country Holdings Limited | Tamworth | 2013 |
| Blackbrook Holdco Limited | Lichfield | 2025 |
| Blackbuck Acquisitions Limited | Luton | 2017 |
| Blackburn & Co. Holdings Limited | Banbury | 2022 |
| Blackburn Enterprise Limited | Stourport On Severn | 2017 |
| Blackburn Group Holdings Ltd | Hartlepool | 2025 |
| Blackburn Holdings Ltd | Stoke-On-Trent | 2022 |
| Blackburn International Holdings Limited | Camberley | 2025 |
| Blackburn Investments Limited | London | 2023 |
| Blackburn With Darwen and Bolton Phase 1 (Refico) Limited | London | 2018 |
| Blackburn With Darwen and Bolton Phase 1 Holdings Limited | London | 2009 |
| Blackburn With Darwen and Bolton Phase 2 (Refico) Limited | London | 2019 |
| Blackburn With Darwen and Bolton Phase 2 Holdings Limited | London | 2010 |
| Blackburne Holdings Limited | Maidenhead | 2024 |
| Blackcap Farms Limited | Lewes | 1998 |
| Blackchair Holdings Limited | Leigh On Sea | 2019 |
| Blackcherry Consulting Ltd | London | 2026 |
| Blackcraig Windfarm Holdings Limited | Edinburgh | 2015 |
| Blackcrest Capital Ltd | London | 2026 |
| Blackcrest Holdings Ltd | Cardiff | 2026 |
| Blackcroft (Holdings) Limited | Glasgow | 2015 |
| Blackcrown Investments Limited | Bolton | 2026 |
| Blackdale Holdings Limited | Waltham Cross | 2023 |
| Blackditch Farms Limited | Oxford | 2017 |
| Blackdog Estate | Burgess Hill | 2017 |
| Blackdog Estate Holdings Ltd | Burgess Hill | 2020 |
| Blackdog Estate Investments Ltd | Burgess Hill | 2018 |
| Blackdog Investments (UK) Limited | Formby | 2010 |
| Blackdoor Ventures Limited | London | 2022 |
| Blackdot Group Ltd | Tring | 2025 |
| Blackdown Asset Management Limited | Southampton | 2024 |
| Blackdown Group Limited | Cullompton | 2018 |
| Blackdown Growers (Holdings) Limited | Leamington Spa | 2023 |
| Blackdown Partners Limited | London | 2019 |
| Blackdynamicgroup Ltd | London | 2025 |
| Blacker Group Ltd | York | 2026 |
| Blacker Holdings Ltd | Plymouth | 2016 |
| Blackerpadel Holdings Ltd | York | 2026 |
| Blacketts of Butterknowle Limited | Newton Aycliffe | 2019 |
| Blackfield Capital Ltd | Manchester | 2026 |
| Blackfields Ltd | Bucks | 2006 |
| Blackfin Capital Partners UK Ltd | London | 2021 |
| Blackfinch Adaptations PLC | Cheltenham | 2018 |
| Blackfinch Asset Management Limited | Cheltenham | 2018 |
| Blackfinch Corporate Services Limited | Cheltenham | 2004 |