| Big BAD Customs Ltd | Other services | 2021 |
| Big Bear Web Studios Ltd | Information & communication | 2023 |
| Big Belfast Events Limited | Hospitality | 2024 |
| Big Block Construction Limited | Construction | 2012 |
| Big Bubba Burgers Ltd | Hospitality | 2015 |
| Big Buffalo Pizza Limited | Hospitality | 2022 |
| Big Business Agency Ltd | Professional & scientific | 2021 |
| Big Cat Ventures Ltd | Information & communication | 2023 |
| Big Deep Datalabs LP | | 2022 |
| Big Dogg Media Ltd | Information & communication | 2019 |
| Big E Retail Limited | Wholesale & retail | 2024 |
| Big Fish Direct Ltd | Hospitality | 2018 |
| Big Fish Films (NI) Ltd | Information & communication | 2010 |
| Big Friendly Giants UK Group Ltd | Professional & scientific | 2023 |
| Big House Creative Ltd | Professional & scientific | 2019 |
| Big Johns Traditional Fish & Chips Ltd | Hospitality | 2026 |
| Big Lily Foundation C.I.C. | Other services | 2017 |
| Big Motive Ltd | Information & communication | 2004 |
| Big Shot Strength Club Ltd | Arts & recreation | 2025 |
| Big Sleep Anaesthetic Services Ltd | Health & social care | 2025 |
| Big Square Limited | Manufacturing | 2023 |
| Big Taste Food Ltd | Hospitality | 2023 |
| Big Top Productions Limited | Hospitality | 1998 |
| Big Tree Joinery Ltd | Manufacturing | 2011 |
| Bight Initiatives CIC | Arts & recreation | 2025 |
| Bigleaf Limited | Hospitality | 2016 |
| Biglolly Limited | Professional & scientific | 2007 |
| Bigqin Technology Co Limited | Wholesale & retail | 2025 |
| Bigrock Digital Ltd | Information & communication | 2010 |
| Bihaona Ltd | Wholesale & retail | 2024 |
| Biild Ltd | Information & communication | 2021 |
| Bijou Body Piercing Ltd | Other services | 2022 |
| Bikemesh Ltd | Manufacturing | 2024 |
| Bilal Group Ltd | Wholesale & retail | 2026 |
| Bill Morrow Fitness Ltd | Arts & recreation | 2022 |
| Biller Genie Software NI, Ltd | Information & communication | 2025 |
| Billions Resources Ltd | Health & social care | 2022 |
| Billy Bloom Ltd | Water & waste | 2024 |
| Billy Gillies Limited | Arts & recreation | 2023 |
| Billy Gillies Publishing Limited | Information & communication | 2024 |
| Billy Goat Entertainment Limited | Information & communication | 2010 |
| BIN Leonardo Ltd | Wholesale & retail | 2025 |
| BIN Mountain Windfarm (N.I.) Limited | Energy | 2003 |
| BIN Mussa International Ltd | Wholesale & retail | 2026 |
| Bin-Ovation Limited | Water & waste | 2012 |
| Binary River Ltd | Information & communication | 2025 |
| Binbin Cool Limited | Wholesale & retail | 2025 |
| Binbulid Feng Co., Ltd | Wholesale & retail | 2024 |
| Binevenagh View Glamping Limited | Hospitality | 2025 |
| Bingi's Kitchen Ltd | Hospitality | 2023 |
| Binian Properties Limited | Real estate | 2007 |
| Binky's Restaurants Ltd | Professional & scientific | 2017 |
| Binkys Belmont Ltd | Hospitality | 2019 |
| Binlee Limited | Wholesale & retail | 2024 |
| Binnacle HR Limited | Administrative & support | 2023 |
| Binneain Limited | Real estate | 2023 |
| Binx&Bella Ltd | Arts & recreation | 2019 |
| BIO Foam Spray Insulation Ltd | Construction | 2022 |
| BIO Search (N.I.) Limited | Professional & scientific | 1989 |
| Bio-Flex Yarns Limited | Manufacturing | 2014 |
| Biobag UK Limited | Wholesale & retail | 2021 |
| Biocidal Solutions Limited | Administrative & support | 2017 |
| Biocolor Limited | Manufacturing | 1992 |
| Biofiltro UK Ltd | Water & waste | 2026 |
| Biofreq Ltd | Wholesale & retail | 2025 |
| Bioheal Ltd | Manufacturing | 2019 |
| Biomarx Ltd | Professional & scientific | 2025 |
| Biomicrohertz Ltd | Wholesale & retail | 2025 |
| Biopanda Reagents Ltd | Manufacturing | 2013 |
| Biopax Limited | Manufacturing | 2018 |
| Bioseer Limited | Professional & scientific | 2023 |
| Biothermo Consultation Ltd | Professional & scientific | 2025 |
| Biovitess Limited | Wholesale & retail | 2020 |
| Biovyteam Limited | Financial services | 2020 |
| Birch Hill Capital Ltd | Financial services | 2016 |
| Birchgrove Properties Limited | Real estate | 2002 |
| Birchill Land Management Limited | Real estate | 2016 |
| Birchwood Grove NI Management Company Limited | Households | 2024 |
| Birchwood Manufacturing Ltd | Manufacturing | 2024 |
| Bird and BUN Ltd | Hospitality | 2025 |
| Bird Golf Ltd | Administrative & support | 2025 |
| Birdies Day Nursery Limited | Health & social care | 2002 |
| Birkdale One Ltd | Wholesale & retail | 2025 |
| Birney Financial Limited | Professional & scientific | 2026 |
| Birota Economics Group UK Limited | Professional & scientific | 2024 |
| Birthdays Limited | | 2006 |
| Biscuit Factory Construction Limited | Construction | 2024 |
| Bishilin Jewelry Limited | Wholesale & retail | 2025 |
| Bishops' Appeal (NI) Limited | Education | 2004 |
| Bislba Limited | Wholesale & retail | 2024 |
| Bisp Training Ltd | Health & social care | 2014 |
| Bistro Marcel Ltd | Hospitality | 2025 |
| Bistro SB Limited | Hospitality | 2015 |
| BIT Byte BIT Software Ltd | Information & communication | 2016 |
| BIT Technologies & Systems Limited | Wholesale & retail | 2020 |
| Bitcoin Construction Ltd | Construction | 2025 |
| Bitneststudio Ltd | Information & communication | 2025 |
| Bitpay Payment Systems Limited | Administrative & support | 2017 |
| Bittles Irish Whiskey Co Ltd | Wholesale & retail | 2018 |
| Biwtec Ltd | Information & communication | 2021 |