| Belfast Minibus Company Limited | Transport & logistics | 2012 |
| Belfast Motors Limited | Wholesale & retail | 2026 |
| Belfast Party Bikes Ltd | Administrative & support | 2023 |
| Belfast Serviced Accomodation Ltd | Real estate | 2019 |
| Belfast TEN Ltd | Real estate | 2023 |
| Bell Rolston Limited | Professional & scientific | 2023 |
| Bellsize Limited | Extraterritorial | 2015 |
| Belmont Gate Management Company Ltd | Households | 2002 |
| BEN Madigan Limited | Real estate | 2023 |
| BEN ORR Racing Limited | Other services | 2019 |
| BES Solutions Limited | Professional & scientific | 2017 |
| Besimple IT Solutions Limited | Information & communication | 2025 |
| Bespoke Diabetes Care Ltd | Health & social care | 2024 |
| Bespoke Plumbing and Heating Limited | Construction | 2017 |
| Besters Food Ltd | Hospitality | 2024 |
| Big 3 Auto Electrical Limited | Wholesale & retail | 2024 |
| Bigsmall Design Limited | Professional & scientific | 2012 |
| BIO Scenes Analytics Ltd | Health & social care | 2019 |
| Birchwood Manor Management Company Limited | Households | 2008 |
| Birds EYE Wall's Limited | | 1972 |
| BJC Group 1 Limited | Construction | 2020 |
| BJC Group Limited | Construction | 2019 |
| BJG Consultancy Ltd | Professional & scientific | 2017 |
| BL 2023 Property Ltd | Households | 2023 |
| Black Mirror Marketing Ltd | Professional & scientific | 2020 |
| Blackcastle Consultancy Services Ltd | Professional & scientific | 2022 |
| Blackdog Media Ltd | Information & communication | 2025 |
| Blackout City Limited | Arts & recreation | 2025 |
| Blackthorn Hollow Management Company Limited | Real estate | 2005 |
| Blanc Bridal Ltd | Other services | 2025 |
| BLK Box Fitness Group Limited | Arts & recreation | 2016 |
| BLK Box Fitness Limited | Manufacturing | 2012 |
| Blue Hammer Home Services Ltd | Construction | 2026 |
| Blue Orchid Home Design Ltd | Construction | 2023 |
| Blue Shark Digital Ltd | Information & communication | 2024 |
| Blue Star Rentals Limited | Extraterritorial | 2011 |
| Blue Wave Fulfillment UK Ltd | Wholesale & retail | 2025 |
| Blueprint Machines NI Limited | Arts & recreation | 2025 |
| BM Roofing Contracts Limited | Construction | 2024 |
| BMC Estates Ltd | Administrative & support | 2009 |
| BMD Builders Ltd | Construction | 2024 |
| BMG Contracts Limited | Construction | 2025 |
| BMG Rigging & Electrical Limited | Construction | 2016 |
| Bond Freight Trading Ltd | Transport & logistics | 2021 |
| Bookkeeping Made Simple Ltd | Professional & scientific | 2011 |
| Boucher Enterprises Limited | Real estate | 2010 |
| Boxpak Holdings Limited | Manufacturing | 2017 |
| BP Ward Ltd | Real estate | 2024 |
| Bradbury Court Limited | Real estate | 1998 |
| Brae Deli Co. Ltd | Hospitality | 2026 |
| Bramble Systems Ltd | Information & communication | 2011 |
| Brankin Engineering Limited | Manufacturing | 1965 |
| Breen Court Management Company (NO. 2) Limited | Households | 2019 |
| Brennan & Lamont Holdings Ltd | Financial services | 2025 |
| Brian J Gallagher Ltd | Professional & scientific | 2006 |
| Brian Rafferty Ltd | Extraterritorial | 2024 |
| Brick and Stone Direct Limited | Wholesale & retail | 2016 |
| Bridge Cabs Glengormley Limited | Transport & logistics | 2020 |
| Bridge Mackie Textile International Ltd | | 2000 |
| Bright Energy Supply NI Limited | Energy | 2018 |
| Bright Sparks Tutoring Limited | Education | 2025 |
| British Asphalt and Bitumen Limited | Financial services | 1931 |
| Brittain Distribution Ltd | Wholesale & retail | 2013 |
| Bronze Booth Ltd | Other services | 2025 |
| Bronze BT2 Ltd | Other services | 2026 |
| Browns Catering Limited | Hospitality | 2020 |
| Bullick Developments (1986) Limited | Real estate | 1986 |
| Bullick Developments (2023) Limited | Real estate | 2023 |
| Business Park Solutions Ltd | Information & communication | 2013 |
| Busy DAD Crew Ltd | Health & social care | 2024 |
| Buttoned Furniture Ltd | Manufacturing | 2021 |
| BVD Darts Limited | Manufacturing | 2022 |
| Bvjv Limited | Construction | 2013 |
| Byrne Law Searchers LLP | | 2006 |
| C Squared Ltd | Information & communication | 2015 |
| C-Link Subs Ltd | Hospitality | 2017 |
| C.H.A. Properties Belfast Ltd | Real estate | 2009 |
| C.J.M. Properties Limited | Real estate | 1995 |
| C.S. Lean Solutions Ltd | Professional & scientific | 2010 |
| C21 Theatre Company Ltd | Arts & recreation | 2005 |
| Caelum Limited | Real estate | 2015 |
| Café Cuisine Catering Ltd | Hospitality | 2025 |
| Cage Gladiators Ireland Ltd | Arts & recreation | 2019 |
| Cailean Developments Ltd | Construction | 2014 |
| Cairn Estates Limited | Real estate | 1946 |
| CAL Events Ltd | Public administration | 2024 |
| Call the Gate MAN Gatefix NI Ltd | Construction | 2022 |
| Callan River Ltd | Health & social care | 2022 |
| CAM Group Facilities Limited | Wholesale & retail | 2023 |
| CAN Services Group Ltd | Wholesale & retail | 2004 |
| CAN YOU EAT IT? Ltd | Information & communication | 2023 |
| Canon (Scotland) Business Machines Limited | | 1996 |
| Capita Managed IT Solutions Limited | Information & communication | 1997 |
| Capital City Rentals Limited | Extraterritorial | 1991 |
| Car Repairs NI Bodyshop Ltd | Wholesale & retail | 2024 |
| Car Servicing Newtownabbey Limited | Wholesale & retail | 2019 |
| Carbon Software Ltd | Wholesale & retail | 2025 |
| Carbrothersni Limited | Wholesale & retail | 2020 |
| Carlincommerce Ltd | Wholesale & retail | 2025 |
| Carn Vehicle Contracts Ltd | Wholesale & retail | 2001 |