| Biyi Ltd | Information & communication | 2023 |
| Biztech Software (NI) Ltd | Information & communication | 2007 |
| Bizvest UK Limited | Administrative & support | 2021 |
| Bizzoe Trading Co Limited | Wholesale & retail | 2025 |
| BJ Haulage Carnagh Ltd | Transport & logistics | 2018 |
| BJJ Construction Ltd | Construction | 2007 |
| BJJ Results Ltd | Health & social care | 2020 |
| BJK Consulting Limited | Professional & scientific | 2017 |
| BJM Hair Limited | Other services | 2018 |
| BJP Services Ltd | Manufacturing | 2019 |
| Bjperry Ltd | Manufacturing | 2025 |
| BK Building (IRL) Ltd | Construction | 2025 |
| BK Company Holdings N.I Ltd | Professional & scientific | 2024 |
| BK Developments Group Limited | Financial services | 2019 |
| Bkce Investments Limited | Financial services | 2018 |
| BKH Limited | Hospitality | 2022 |
| BKS Belfast Ltd | Hospitality | 2025 |
| BKT Engineering Ltd | Manufacturing | 2020 |
| BL Broxburn Limited | Other services | 2006 |
| BL Chesser Limited | Other services | 2006 |
| BL Engineering Limited | Administrative & support | 2001 |
| BL Sighthill Limited | Administrative & support | 2006 |
| BL Skip Hire Limited | Water & waste | 2026 |
| BL Waste Management Limited | Water & waste | 2026 |
| Black Art Stunts Ltd | Information & communication | 2016 |
| Black AXE Throwing Company Limited | Arts & recreation | 2024 |
| Black Copper Design Company Ltd | Professional & scientific | 2018 |
| Black Crowes Films Limited | Information & communication | 2023 |
| Black EYE Technology Limited | Information & communication | 2013 |
| Black Horse Performance Ltd | Wholesale & retail | 2025 |
| Black Lion Capital LP | | 2025 |
| Black Mountain Developers Limited | Construction | 2025 |
| Black Mountain N.I Ltd | Construction | 2026 |
| Black Mountain Shared Space | Administrative & support | 2017 |
| Black Mountain Trading Limited | Real estate | 2019 |
| Black Mountain Training Services C.I.C. | Professional & scientific | 2020 |
| Black Mountain ZEN Centre | Administrative & support | 2016 |
| Black Seal Developments Limited | Construction | 2006 |
| Black Stone Industries Ltd | Other services | 2016 |
| Black Storm Consultants Ltd | Information & communication | 2020 |
| Black Swan Impact Ltd | Information & communication | 2014 |
| Black Thunder Boxing Ltd | Arts & recreation | 2026 |
| Blackbird Concepts Ltd | Financial services | 2022 |
| Blackbourne Limited | Construction | 1970 |
| Blackburne Property Developments Limited | Real estate | 1998 |
| Blackburnhydro Limited | Construction | 2016 |
| Blackdog (N.I.) Limited | | 2002 |
| Blackened Heart Ltd | Wholesale & retail | 2023 |
| Blackest Ever Black Films Ltd | Information & communication | 2026 |
| Blackfire Food Ltd | Manufacturing | 2021 |
| Blackfort Joiners Ltd | Construction | 2013 |
| Blackhorse Capital Group Ltd | Financial services | 2025 |
| Blackie River Community Groups | Education | 1999 |
| Blackjade Finance Ltd | Financial services | 2024 |
| Blacklion Capital Group Ltd | Financial services | 2025 |
| Blackmore Quoile Crescent Limited | Construction | 2013 |
| Blackpearl Real Estate LLP | | 2009 |
| Blackpearl Tattoo Lounge Ltd | Arts & recreation | 2025 |
| Blackquarter Lane Management Company Limited | Extraterritorial | 2006 |
| Blackquarterav Ltd | Construction | 2015 |
| Blackridge Enterprises Ltd | Financial services | 2025 |
| Blackrock Hollow Management Limited | Households | 2018 |
| Blacks Road Service Station Ltd | Wholesale & retail | 2002 |
| Blacks Wines Ltd | Wholesale & retail | 2012 |
| Blacksheep NI Ltd | Manufacturing | 1975 |
| Blackspace&Uk Limited | Wholesale & retail | 2024 |
| Blackstaff (Holdings) Ltd | Financial services | 2017 |
| Blackstaff Communications Ltd | Information & communication | 1993 |
| Blackstaff Court Management Company Limited | Households | 2000 |
| Blackstaff Diagnostics Ltd | Health & social care | 2019 |
| Blackstaff Ecology Ltd | Professional & scientific | 2012 |
| Blackstaff Games Ltd | Information & communication | 2014 |
| Blackstaff Grappling Ltd | Education | 2023 |
| Blackstaff House Management Company Limited | Households | 2000 |
| Blackstaff Trading Limited | Extraterritorial | 2021 |
| Blackstar Forex Networks Inc Limited | Other services | 2013 |
| Blackstown Limited | Real estate | 2014 |
| Blackstyle Industries L.P. | | 2018 |
| Blackwater Land Limited | Extraterritorial | 1996 |
| Blackwell Associates Limited | Health & social care | 2014 |
| Blackwood Court Apartments Management Company Limited | Households | 2018 |
| Bladderwort Limited | Wholesale & retail | 2025 |
| Blades (N.I.) Ltd | Other services | 2025 |
| Blades Belfast Ltd | Real estate | 2016 |
| Blades Gents Barbers (N.I.) Ltd | Other services | 2025 |
| Bladeworx NI Limited | Wholesale & retail | 2024 |
| Bladon Park Management Company Limited | Households | 2015 |
| Bladon Ventures Ltd | Professional & scientific | 2013 |
| Blain Developments Ltd | Real estate | 2025 |
| Blair Group Industries Limited | Real estate | 2019 |
| Blair House Limited | Health & social care | 2004 |
| Blakiston Houston Estate Company Limited | Agriculture & fishing | 1926 |
| Blanche Retail Nomine Limited | Wholesale & retail | 2023 |
| Blaney Inns Limited | Hospitality | 2013 |
| Blaney Mccartan Ltd | Health & social care | 2008 |
| Blaneys Engineering Ltd | Professional & scientific | 2026 |
| Blank Restaurants Limited | Hospitality | 2021 |
| Blaris (Fields and Lane) Management Company Limited | Households | 2017 |
| Blaris Developments Limited | Construction | 2013 |
| Blaris Meadows Estate Management Company Limited | Households | 2015 |