| Bsni Ltd | Professional & scientific | 2011 |
| BT 127 Limited | Real estate | 2025 |
| BT Games Limited | Wholesale & retail | 2026 |
| BT Sandwhich Co Limited | Hospitality | 2026 |
| BT15 Ltd | Real estate | 2024 |
| BT17 Limited | Agriculture & fishing | 2016 |
| BT2 Property Ltd | Real estate | 2017 |
| BT3 Accountants Limited | Professional & scientific | 2011 |
| BT48.COM Ltd | Information & communication | 2012 |
| BT9 Barbers Limited | Other services | 2016 |
| BTA Electrics Ltd | Construction | 2010 |
| BTA Pharm Limited | Wholesale & retail | 2011 |
| BTD Restaurants Ltd | Hospitality | 2014 |
| Bteco Limited | Information & communication | 2014 |
| BTI Systems UK Limited | Professional & scientific | 2008 |
| BTK Services Ltd | Construction | 2016 |
| BTL Marketing Ltd | Professional & scientific | 2014 |
| BTP Books Ltd | Information & communication | 2022 |
| BTS Recovery Ltd | Wholesale & retail | 2016 |
| BUA Healthcare Services Ltd | Health & social care | 2025 |
| Bubba Digital Limited | Information & communication | 2020 |
| Bubble and Beam Ltd | Professional & scientific | 2025 |
| Buchanan (Wholesale) Ltd | Wholesale & retail | 1969 |
| Buchanan Johnston Flynn Limited | Financial services | 2004 |
| Buchanan-Ni.Org | Information & communication | 2002 |
| Bucket Economics Limited | Information & communication | 2019 |
| Buckets Investment Company | Financial services | 2026 |
| Budget Energy Limited | Energy | 2009 |
| Budibase Ltd | Information & communication | 2019 |
| Budlite Healthcare Ltd | Health & social care | 2022 |
| Budlite Security & Facility Management Ltd | Administrative & support | 2021 |
| Budore Ground Services Ltd | Administrative & support | 2018 |
| Buffalo Belfast Ltd | Hospitality | 2023 |
| Buick Media Limited | Financial services | 2026 |
| Build for YOU Group Ltd | Construction | 2024 |
| Build Simply Ltd | Wholesale & retail | 2024 |
| Buildflowmedia Ltd | Professional & scientific | 2025 |
| Building Automation Controls Ltd. | Manufacturing | 2011 |
| Building Consultancy Services Limited | Professional & scientific | 2015 |
| Building Service Group LP | | 2018 |
| Building Services Academy Community Interest Company | Education | 2017 |
| Building Solutions Ireland Limited | Construction | 2016 |
| Bukmark Merchandising Ltd | Wholesale & retail | 2025 |
| Bull and Bear Ventures Ltd | Financial services | 2025 |
| Bull Screens Ltd | Professional & scientific | 2026 |
| Bulldog Xtreme Limited | Extraterritorial | 2017 |
| Bullhouse Bar Company Limited | Hospitality | 2021 |
| Bullhouse Brewing Company Limited | Manufacturing | 2017 |
| Bullitt Holding Limited | Financial services | 2018 |
| Bullitt Trading Limited | Hospitality | 2018 |
| Bullseye Pest Control Ltd | Administrative & support | 2018 |
| BULTEX99 Ltd | Wholesale & retail | 2025 |
| Bulwark Guarding Ltd | Administrative & support | 2024 |
| Bumbleb Assets Ltd | Information & communication | 2021 |
| Bumbles Daycare Limited | Health & social care | 2014 |
| Bumbrella Corporation Limited | Wholesale & retail | 2025 |
| Bump Accident Management Ltd | Other services | 2025 |
| Bump Films Limited | Information & communication | 2018 |
| Bunny Investments Limited | Professional & scientific | 1997 |
| BUR Ranting Limited | Wholesale & retail | 2024 |
| Burakparlak Limited | Wholesale & retail | 2024 |
| Burbridge Ducann LLP | | 2010 |
| Burcott Trust Limited | Administrative & support | 1998 |
| Burger Crew Ltd | Hospitality | 2023 |
| Burges Salmon (Northern Ireland) Limited | Professional & scientific | 2012 |
| Burghley Mews Management Limited | Households | 2006 |
| Burin Limited | Wholesale & retail | 2025 |
| Burkard Jens Ltd | Wholesale & retail | 2024 |
| Burke Financial Planning Ltd | Financial services | 2024 |
| Burke Systems & Solutions Limited | Information & communication | 2013 |
| Burkey.L Ltd | Wholesale & retail | 2023 |
| Burnbank Residents Ltd | Households | 2025 |
| Burney Mews Limited | Extraterritorial | 1982 |
| Burns & Co Legal Limited | Professional & scientific | 2018 |
| Burns Dewar Legal Limited | Professional & scientific | 2024 |
| Burns IT Solutions Ltd | Wholesale & retail | 2011 |
| Burnside Manor Management Limited | Households | 2005 |
| Burnside Music Services Ltd | Information & communication | 2023 |
| Burnview Care Management Limited | Health & social care | 2022 |
| Burnview Healthcare Limited | Administrative & support | 2012 |
| Burnview Holdings Limited | Financial services | 2016 |
| Burnview Properties Limited | Construction | 1996 |
| Burnview Shoes Ltd | Wholesale & retail | 2001 |
| Buroashe Limited | Professional & scientific | 2020 |
| Bursitis Limited | Wholesale & retail | 2025 |
| Bury Glass Ltd | Construction | 2026 |
| Bush Demesne Antrim Management Company Ltd | Construction | 2014 |
| Bush Farm Foods Ltd | Agriculture & fishing | 2023 |
| Bush View Management Company Limited | Real estate | 2021 |
| Bushmills Mineral Water Ltd | Other services | 2015 |
| Bushview Developments Limited | Construction | 2009 |
| Bushwhack Limited | Wholesale & retail | 2025 |
| Business Accountancy Services (NI) Limited | Professional & scientific | 2012 |
| Business Capital & Finance (ATL) Limited | Financial services | 2019 |
| Business Capital & Finance (DR1) Limited | Financial services | 2019 |
| Business Capital & Finance (SD1) Limited | Financial services | 2020 |
| Business Capital and Finance (PC) Limited | Financial services | 2019 |
| Business Capital and Finance Limited | Financial services | 2016 |
| Business Compliance Solutions Ltd | Wholesale & retail | 2007 |
| Business Computers Hillsborough Limited | Information & communication | 1986 |