| Lockdown Storage Limited | Transport & logistics | 2020 |
| Locked Groove Ltd | Professional & scientific | 2013 |
| Lodge Farm (Bearpark) Management Company Limited | Households | 2014 |
| Lofty Solution Limited | Construction | 2018 |
| Logicalmetricsai Ltd | Information & communication | 2025 |
| Logicli Limited | Information & communication | 2025 |
| LOK Healthcare Limited | Health & social care | 2023 |
| Lola's Glamcam Model Ltd | Information & communication | 2024 |
| Lomax Living Limited | Real estate | 2022 |
| Lomond Construction Services Limited | Construction | 2026 |
| Lonbar Construction & Maintenance Ltd | Construction | 2022 |
| Lonex Group Limited | Information & communication | 2026 |
| Longstaff Leisure Ltd | Arts & recreation | 2025 |
| Lopario Shen Ltd | Information & communication | 2024 |
| Lord's Pantry Ltd | Wholesale & retail | 2021 |
| Lorna Welch Developments (Durham) Ltd | Real estate | 2025 |
| Lorna Welch Developments (West Rainton) Ltd | Real estate | 2025 |
| Lorna Welch Developments Limited | Construction | 2023 |
| Lorvex Limited | Wholesale & retail | 2025 |
| Lost Flying Club Ltd | Professional & scientific | 2023 |
| Louise Anglicas Ltd | Information & communication | 2008 |
| Lou’S Ecoclean Services Ltd | Administrative & support | 2025 |
| Loved Always Ltd | Manufacturing | 2026 |
| Lovert Ltd | Wholesale & retail | 2025 |
| Loveyourmoves Ltd | Real estate | 2019 |
| Lovingly Engineered Architectural Practice Limited | Professional & scientific | 2023 |
| Lovingly Engineered Architecture Limited | Professional & scientific | 2022 |
| LOW Butterby Ltd | Agriculture & fishing | 2020 |
| LOW Meadows (Witton Gilbert) Management Company Limited | Households | 2009 |
| LOW Meadows Equestrian Centre Limited | Agriculture & fishing | 2010 |
| Lowerson Groundworks Limited | Construction | 2016 |
| Lowther's Durham Limited | Hospitality | 2018 |
| Loyaltek UK Ltd | Information & communication | 2021 |
| LP North Two Limited | Wholesale & retail | 2022 |
| LS Global Consultants Ltd | Professional & scientific | 2024 |
| LSC PUB Co Ltd | Hospitality | 2025 |
| LSH Leisure Pubs Ltd | Hospitality | 2026 |
| LSL Construction Ltd | Construction | 2020 |
| LSP Pharm Ltd | Health & social care | 2025 |
| LSS North East Ltd | Real estate | 2023 |
| LT Consulting Ltd | Information & communication | 2021 |
| LTC International Logistics Limited | Transport & logistics | 2017 |
| Lucas Worldwide Ltd | Wholesale & retail | 2020 |
| Lucios (Cleadon) Ltd | Hospitality | 2022 |
| Lucios Ltd. | Hospitality | 2017 |
| Lucky 8 Chinese Limited | Hospitality | 2025 |
| Lucky Duck Enterprises Limited | Real estate | 2019 |
| Lucky HE 8 Ltd | Hospitality | 2025 |
| Ludworth Moto X Ltd | Arts & recreation | 2026 |
| Luke S Property Limited | Real estate | 2025 |
| Luma Trade Ltd | Wholesale & retail | 2024 |
| Lumi Insights Ltd | Information & communication | 2023 |
| Lumiere Glow Mist Trading Ltd | Wholesale & retail | 2026 |
| Lumira Group Ltd | Wholesale & retail | 2025 |
| Lumra Ltd | Wholesale & retail | 2025 |
| Lumsden & Carroll Limited | Construction | 2007 |
| Luna Civils & Earth Movers Limited | Construction | 2019 |
| Lunamoth Music Limited | Information & communication | 2012 |
| Lunaria Finance Ltd | Financial services | 2018 |
| Lunated Limited | Hospitality | 2025 |
| Lupfaw 521 Limited | Professional & scientific | 2019 |
| Lush Homes Ltd. | Construction | 2016 |
| Lustre Pearls and Gems Ltd | Wholesale & retail | 2025 |
| Lustre Property Group Ltd | Real estate | 2025 |
| LUU Nguyen Ltd | Other services | 2022 |
| Luvai Consulting Ltd | Health & social care | 2017 |
| Luvi Limited | Wholesale & retail | 2025 |
| LUX Fero Ltd | Professional & scientific | 2025 |
| LUX Nova Properties Ltd | Households | 2025 |
| Luxe Aesthetics by Lucy Limited | Other services | 2022 |
| Luxenest Rentals Ltd | Real estate | 2025 |
| Luxora Linh Limited | Real estate | 2026 |
| Luyiya Global (UK) Co. Ltd | Wholesale & retail | 2010 |
| LV Blue EYE Limited | Hospitality | 2026 |
| Lvac Community Interest Company | Education | 2023 |
| Lydon Pharmacy Group Ltd. | Wholesale & retail | 2000 |
| Lyfe Belts and Bags Ltd | Manufacturing | 2019 |
| Lymph Solutions Ltd | Health & social care | 2019 |
| Lyndsey Deane Ltd | Administrative & support | 2024 |
| Lynwood Professional Services Limited | Professional & scientific | 1991 |
| LZR Holdings Limited | Professional & scientific | 2018 |
| M & a Banks Limited | Construction | 2011 |
| M & a Transportation Limited | Transport & logistics | 2025 |
| M & K Brickwork NE Ltd | Construction | 2019 |
| M & M Grieves Limited | Hospitality | 2004 |
| M & M Groundworks (NE) Limited | Construction | 2014 |
| M & P Properties (NE) Limited | Real estate | 2023 |
| M and M Safety Services Limited | Professional & scientific | 2004 |
| M F Pointing Limited | Construction | 2016 |
| M F Renneberg Limited | Construction | 2008 |
| M J Plaster & Building Contractor & Sons Limited | Construction | 2016 |
| M M Wind Services Ltd | Construction | 2025 |
| M O B Utilities Ltd | Construction | 2023 |
| M Pace Painters & Decorators Limited | Construction | 2017 |
| M W Construction (NE) Limited | Construction | 2015 |
| M Wilkinson Engineering Ltd | Professional & scientific | 2014 |
| M&C Watson Holdings Ltd | Financial services | 2019 |
| M&F Groundworks Ltd | Construction | 2024 |
| M&G Properties (NE) Limited | Real estate | 2016 |
| M&H Consultants Limited | Professional & scientific | 2014 |