| Kynza Ltd | Health & social care | 2022 |
| Kyoto Enterprises Ltd | Wholesale & retail | 2012 |
| KYP Hospitality Group Ltd | Hospitality | 2025 |
| Kytchin Creatve Ltd | Wholesale & retail | 2025 |
| L & Q Holdings Ltd | Financial services | 2017 |
| L & T Cleaning Solutions Ltd | Administrative & support | 2024 |
| L 2 Developments Limited | Construction | 2007 |
| L and C Rigging Limited | Construction | 2023 |
| L B Catering (2024) Ltd | Hospitality | 2024 |
| L G Cooke Construction Limited | Construction | 2021 |
| L H Executive Chauffeurs Ltd | Transport & logistics | 2020 |
| L J Braid Ltd | Manufacturing | 2026 |
| L J Consultancy Ltd | Other services | 2016 |
| L K Gibson Consultancy Ltd | Other services | 2017 |
| L Moore Properties Ltd | Real estate | 2019 |
| L S Creches Limited | Education | 2011 |
| L&A Infinity Ltd | Real estate | 2021 |
| L&A Painting & Decorating Ltd | Construction | 2016 |
| L&B (NO 86) Limited | Construction | 2005 |
| L&B (NO.16) | Financial services | 2002 |
| L&M Fabrications Ltd | Construction | 2018 |
| L&P Properties Limited | Real estate | 2025 |
| L&S Property Services Ltd | Real estate | 2018 |
| L'Academie Management Limited | Extraterritorial | 1996 |
| L'Arche Belfast | Health & social care | 2001 |
| L. Herbert & SON, Limited | Extraterritorial | 1949 |
| L.A.S Caravan Brokerage Ltd | Wholesale & retail | 2013 |
| L.A.S Motorhome and Caravan Brokerage Ltd | Administrative & support | 2013 |
| L.H.R. Engineering Ltd | Manufacturing | 2016 |
| L.M.G. Properties Limited | Construction | 1998 |
| L.P.I (Blantyre) Ltd | Real estate | 2022 |
| L.P.I (Denaby) Ltd | Real estate | 2014 |
| L.P.I (Gatherley) Ltd | Real estate | 2016 |
| L.P.I (Nairn) Ltd | Real estate | 2014 |
| L.P.I (Properties) Ltd | Real estate | 2010 |
| L.P.I (Sprucefield) Ltd | Real estate | 2013 |
| L.P.I (Stirling) Limited | Real estate | 2016 |
| L.P.I (Tranent) Ltd | Real estate | 2023 |
| L.T. Byrne Law Searchers Limited | Professional & scientific | 2001 |
| LA Babalu Limited | Wholesale & retail | 1975 |
| LA Cuisine Catering Co Ltd | Hospitality | 2001 |
| LA Distribution (NI) Ltd | Wholesale & retail | 1998 |
| LA Picante Ltd | Wholesale & retail | 2026 |
| LA Prive Ltd | Wholesale & retail | 2026 |
| LA Riche Europe Limited | Manufacturing | 2025 |
| LA Sala Limited | Financial services | 2025 |
| LA Table Ltd | Wholesale & retail | 2025 |
| LA Torre Francesco Ltd | Wholesale & retail | 2025 |
| LAB & Process Instrumentation Ltd | Professional & scientific | 2002 |
| LAB Fitness N.I. Ltd | Arts & recreation | 2024 |
| Laban Investments Limited | Extraterritorial | 2004 |
| Labceutics Ltd | Professional & scientific | 2011 |
| Labistyle Partners LP | | 2018 |
| Lablynx Limited | Health & social care | 2023 |
| Labour in Faith & Trust | Construction | 2017 |
| Lacey & Co Solicitors Limited | Professional & scientific | 2020 |
| Lacheery International Limited | Wholesale & retail | 2026 |
| Lack Peter Ltd | Wholesale & retail | 2024 |
| LAD Property Holdings Ltd | Real estate | 2022 |
| Ladas Management Limited | Other services | 2006 |
| Ladbrokes (Northern Ireland) (Holdings) Limited | Financial services | 1993 |
| Ladbrokes (Northern Ireland) Limited | Extraterritorial | 2004 |
| Lady Dunwell Limited | Real estate | 2025 |
| Ladybird and BEE Series One Limited | Information & communication | 2020 |
| Ladybird and BEE Series Two Limited | Information & communication | 2022 |
| Lagan (Edinburgh) Limited | Construction | 2015 |
| Lagan (Hillsborough) Ltd | Extraterritorial | 2023 |
| Lagan 105 Limited | Extraterritorial | 1999 |
| Lagan 106 Limited | Mining & quarrying | 1976 |
| Lagan Agile Limited | Professional & scientific | 2026 |
| Lagan AGL Limited | Construction | 2026 |
| Lagan Airport Maintenance Limited | Construction | 2017 |
| Lagan Airsoft Limited | Arts & recreation | 2016 |
| Lagan Aviation & Infrastructure Group Holdings Limited | Construction | 2017 |
| Lagan Aviation & Infrastructure Limited | Construction | 2014 |
| Lagan Backpackers Ltd | Hospitality | 2016 |
| Lagan Barrier Solutions Limited | Construction | 2014 |
| Lagan Beverages Limited | Hospitality | 2017 |
| Lagan Boat Company (N.I.) Ltd | Transport & logistics | 2001 |
| Lagan Building Contractors Limited | Construction | 2011 |
| Lagan Building Services Consulting Ltd | Professional & scientific | 2023 |
| Lagan Cement Group Limited | Professional & scientific | 1983 |
| Lagan College Education Partnership (Holdings) Limited | Financial services | 2010 |
| Lagan College Education Partnership Limited | Financial services | 2010 |
| Lagan College Limited | Education | 1981 |
| Lagan Communications Ltd | Professional & scientific | 2021 |
| Lagan Construction Group Holdings Limited | Professional & scientific | 2009 |
| Lagan Construction Group Limited | Construction | 2011 |
| Lagan Construction Limited | Construction | 1962 |
| Lagan Construction Services Limited | Mining & quarrying | 1975 |
| Lagan Contracts Ltd | Wholesale & retail | 2025 |
| Lagan Crawl Limited | Construction | 2020 |
| Lagan Demolition Limited | Professional & scientific | 2011 |
| Lagan Dragons Limited | Arts & recreation | 2021 |
| Lagan Electrical Solutions Limited | Extraterritorial | 2015 |
| Lagan Energy (Antrim) Limited | Energy | 2022 |
| Lagan Energy (Ballymena) Limited | Energy | 2021 |
| Lagan Energy (Ballyvallagh) Limited | Energy | 2021 |
| Lagan Energy (Lurgan) Limited | Energy | 2021 |
| Lagan Energy Group Limited | Financial services | 2025 |