| Black Stone Property Lettings Ltd | Blackburn | 2023 |
| Black Stuff Prints Ltd | London | 2024 |
| Black Swan PMC Limited | Coventry | 2020 |
| Black Swiss Mountain Ltd | London | 2021 |
| Black Tree Company Norway Limited | London | 2022 |
| Black Tulip Port ST. George Bahamas Limited | Loughborough | 2022 |
| Black Watch Documentaries Limited | Wakefield | 2003 |
| Black Wolf 0 Ltd | London | 2023 |
| Black-Out! Worldwide Ltd. | Hertfordshire | 1995 |
| Blacka Cases Limited | Whitchurch | 2010 |
| Blacka Group Limited | Whitchurch | 2014 |
| Blacka Hire Limited | Whitchurch | 2014 |
| Blacka Installations Limited | Whitchurch | 2014 |
| Blackarmor Ltd | Chilcompton | 2015 |
| Blackaton Manor Farm (Widecombe) Limited | Newton Abbot | 2022 |
| Blackbank Airsoft Tactical Ltd | Liverpool | 2013 |
| Blackbeard Sailing Limited | London | 2026 |
| Blackberry Clinic (Ipswich) Limited | London | 2016 |
| Blackberry Farm Shop Ltd | South Godstone | 2014 |
| Blackberry Lane Property Management Limited | Coventry | 2019 |
| Blackbird 1964 Limited | Stoke-On-Trent | 2013 |
| Blackbolt Enterprises Ltd | Bristol | 2020 |
| Blackbrook Commodities Ltd | London | 2017 |
| Blackbrook Investments Ltd | Exeter | 2011 |
| Blackburn Products Company Limited | Sheffield | 1919 |
| Blackcliffe Farm Ltd | Nottingham | 2016 |
| Blackcoat Limited | Beccles | 2006 |
| Blackden Walk 1962 Limited | Wilmslow | 2014 |
| Blackdown Hills Business Association | Taunton | 2003 |
| Blackdown Planning Partnership Ltd. | Yeovil | 2018 |
| Blackdown Properties Limited | Taunton | 1991 |
| Blackdragon Films Limited | Southampton | 2025 |
| Blackfield Associates Limited | Portsmouth | 2017 |
| Blackfin Limited | Tunbridge Wells | 2017 |
| Blackflame Limited | London | 1979 |
| Blackford 15 Limited | Frenchay | 2009 |
| Blackford Building Company Limited | Edinburgh | 1982 |
| Blackfriars Court Management Company Limited | Lowestoft | 2012 |
| Blackfriars Leasing Ltd. | Liverpool | 1983 |
| Blackfriars Medieval Garden Community Interest Company | Newcastle | 2009 |
| Blackfriars Radio Limited | Elstree, Borehamwood | 1960 |
| Blackgrass Design Engineering Limited | Londonderry | 2012 |
| Blackheath Lofts & Design Ltd | London | 2022 |
| Blackheath Stamps Ltd | Wisbech | 2021 |
| Blackhill Quarries Ltd | Omagh | 2008 |
| Blackhills Developments Limited | Chessington | 2013 |
| Blackhole Property Developments Ltd | Leigh On Sea | 2025 |
| Blackhorse Capital Ltd | London | 2016 |
| Blackhorse Distribution Limited | Witham | 1986 |
| Blackhouse Investment Properties Limited | London | 2009 |
| Blackie 1960 Limited | Middlesbrough | 2014 |
| Blackleigh Limited | London | 1974 |
| Blackleys Ltd | Axbridge | 2018 |
| Blacklight Associates Limited | Hereford | 2019 |
| Blacklock and Gilchrist Limited | Rainhill | 2025 |
| Blackmore Vale Publishing Company Limited | Liverpool | 1987 |
| Blackney Limited | Alcester | 2013 |
| Blacknight Records Limited | Ashford | 2002 |
| Blackpool Damp Proofing (Lancs) Ltd | Liverpool | 2026 |
| Blackpool Markets Limited | Leeds | 1992 |
| Blackpool Pier Swim Ltd | Blackpool | 2018 |
| Blackquarter Lane Management Company Limited | Belfast | 2006 |
| Blackrock Court Management Services Ltd | Portstewart | 2002 |
| Blackrock Rivers Limited | Harrogate | 2025 |
| Blacks Autos Limited | Gateshead | 2007 |
| Blacks Connect Limited | Leeds | 2012 |
| Blacks London Limited | Wetherby | 1998 |
| Blacks Visual Merchandising (Holdings) Limited | Wetherby | 2003 |
| Blacksea Yachting Ltd | London | 2025 |
| Blacksgrove 1968 Limited | Ballymena | 2013 |
| Blacksmith Corner Apartments Ltd | Ballyclare | 2008 |
| Blacksmiths Court Limited | Bedford | 2003 |
| Blacksmiths Yard Management Company Limited | Nuneaton | 2005 |
| Blackspire Holdings Ltd | Glasgow | 2022 |
| Blackstaff Trading Limited | Belfast | 2021 |
| Blackstone (SH) Ltd | Bolton | 2025 |
| Blackstowe Ltd | Bristol | 2026 |
| Blackswan Property Limited | Birmingham | 2012 |
| Blackswan Yachting Ltd | Blackpool | 2024 |
| Blackthorn Gardens Limited | Northampton | 2016 |
| Blackthorn Ireland Ltd | Newtownards | 2007 |
| Blackthorn Terrace Company Limited | Magherafelt | 2022 |
| Blackthorne 1968 Limited | Smethwick | 2014 |
| Blackthorne Projects Limited | Newcastle Upon Tyne | 2012 |
| Blackthorns 62 Limited | Brierley Hill | 2017 |
| Blacktower Nordic Limited | London | 2010 |
| Blackwatch Industries Ltd | Enniskillen | 2000 |
| Blackwater Land Limited | Belfast | 1996 |
| Blackwater Partners Limited | Chelmsford | 2013 |
| Blackwater Yachting Ltd | Blackpool | 2023 |
| Blackwell (Trustees) Limited | London | 1982 |
| Blackwell Hydraulics Limited | Bristol | 1979 |
| Blackwood Asset Management Limited | Tamworth | 2026 |
| Blackwood Bloodstock Limited | Tamworth | 2024 |
| Blackwood Capital Investments Limited | Tamworth | 2024 |
| Blackwood Capital Ltd | Ashford | 2025 |
| Blackwood Consulting Group Ltd | London | 2021 |
| Blackwood EMC Ltd | Cheltenham | 2003 |
| Blackwood Management Company Limited | Bangor | 2001 |
| Blade Yachting Ltd | Cardiff | 2025 |