| Leah Property Limited | Construction | 2007 |
| Leaps and Bounds North East Limited | Health & social care | 2021 |
| Learning & Skills for Business Ltd | Professional & scientific | 2024 |
| Learning North East Limited | Education | 1999 |
| Learning World Limited | Education | 1994 |
| LEE Joseph Jackson Ltd | Extraterritorial | 2024 |
| LEE Mather Ltd | Information & communication | 2019 |
| LEE Phillpot Logistics Ltd | Transport & logistics | 2025 |
| Legacy Vision LLP | | 2019 |
| Legend Gents TK Limited | Other services | 2022 |
| Legends Gents (AK) Ltd | Other services | 2019 |
| Legendz Barberz Herrington Ltd | Other services | 2022 |
| Legra Design Limited | Wholesale & retail | 2020 |
| Legs Creative Arts C.I.C. | Arts & recreation | 2015 |
| Leighton Management Limited | Professional & scientific | 1988 |
| Leila Hexham Ltd | Wholesale & retail | 2021 |
| LEK Financial Services Limited | Financial services | 2025 |
| Lekka Traders Limited | Wholesale & retail | 2018 |
| Lemondriveenterprises Ltd | Financial services | 2024 |
| Lemonfield Hotel Limited | Hospitality | 2025 |
| Lemphil Limited | Wholesale & retail | 2020 |
| Lenfrank Estates Ltd | Real estate | 2026 |
| Lennox Group Holdings Ltd | Professional & scientific | 2023 |
| Leolin Limited | Hospitality | 2010 |
| Leon Project Community Interest Company | Arts & recreation | 2023 |
| Leonsdelivery Ltd | Transport & logistics | 2026 |
| Lerato Procurement Limited | Wholesale & retail | 2026 |
| LES Potts 4 Wheel Drive Ltd | Wholesale & retail | 1996 |
| Leslie Abrahams Limited | Administrative & support | 2001 |
| LET 2 Own Ltd | Real estate | 2017 |
| LET Developments Limited | Real estate | 2007 |
| LET to LET North East Limited | Real estate | 2025 |
| Let's Go Retro Limited | Other services | 2019 |
| Letterbox Dog Treats Ltd | Wholesale & retail | 2023 |
| Lettings North East Ltd | Financial services | 2025 |
| Letts LET Limited | Real estate | 2013 |
| Levostack Limited | Information & communication | 2016 |
| LEW Trading Ltd | Other services | 2007 |
| Lewis Button Wind Ltd | Manufacturing | 2026 |
| Lewis Paige Limited | Manufacturing | 2003 |
| Lewis Rushworth Ltd | Other services | 2018 |
| Lewu Company Limited | Professional & scientific | 2021 |
| LFR Estates Ltd | Real estate | 2022 |
| LGM Enterprise Ltd | Hospitality | 2025 |
| LGT Property Developments Limited | Real estate | 2016 |
| LH Electrical Services Ltd | Construction | 2015 |
| LH Holdings Group Ltd | Financial services | 2025 |
| Lhmedia Ltd | Information & communication | 2024 |
| LHS Entertainment Ltd | Arts & recreation | 2026 |
| Liadz Leisure Limited | Hospitality | 2008 |
| Liddle Builders Ltd | Financial services | 2017 |
| Liddle Engineering Solutions Ltd | Professional & scientific | 2024 |
| Liddle Foil Blocking Ltd | Manufacturing | 2018 |
| Liebherr Sunderland Works Limited | Manufacturing | 2000 |
| Liege Services Ltd | Professional & scientific | 2026 |
| Life IS Life Limited | Professional & scientific | 2021 |
| Lifestyle Mortgages Ltd | Financial services | 2021 |
| Lift Engineers (UK) Ltd | Manufacturing | 2024 |
| Lift Worx (UK) Ltd | Construction | 2019 |
| Light Fabrication Limited | | 1947 |
| Lighthouse Cleaners Limited | Administrative & support | 2023 |
| Lighthouse Social Care Services Limited | Health & social care | 2014 |
| Lihiniya Gems Ltd | Wholesale & retail | 2019 |
| Liking Sunderland Ltd | Hospitality | 2017 |
| Lilac Street Limited | Administrative & support | 2024 |
| Lileecreation Ltd | Professional & scientific | 2026 |
| Lilety Homes Limited | Real estate | 2025 |
| Lilla the Label Ltd | Wholesale & retail | 2025 |
| Lilley Dogs Ltd | Agriculture & fishing | 2025 |
| Lillian's Blinds Limited | Manufacturing | 2013 |
| Lily Pearl Holdings Ltd | Financial services | 2022 |
| Lilypad Financial Planning Ltd | Financial services | 2018 |
| Limani Properties Ltd | Households | 2025 |
| Lime Leisure (Sunderland) Ltd | Hospitality | 2016 |
| Lime Leisure Limited | Hospitality | 2013 |
| Limitless Properties (North East) Limited | Real estate | 2016 |
| Limitless Sea Fishing Limited | Wholesale & retail | 2022 |
| Lindsay Marie Hurst Limited | Professional & scientific | 2020 |
| Lingsun Ltd | Hospitality | 2025 |
| Linguistic Insights Limited | Professional & scientific | 2022 |
| Linka Group Ltd | Financial services | 2022 |
| Linsley & Turner Properties Limited | Real estate | 2020 |
| Lionfeather Project CIC | Education | 2025 |
| Lisa Bewick the Prior Ltd | Hospitality | 2024 |
| Lister Building Services Ltd | Construction | 2023 |
| Listndrive Ltd | Information & communication | 2026 |
| Litt Recruitment Group Limited | Administrative & support | 2022 |
| Little Bird Hair Design Ltd | Other services | 2025 |
| Little Black Dog Software Ltd | Information & communication | 2017 |
| Little Bolton Terrace East RTM Company | Households | 2023 |
| Little Bolton Terrace West RTM Company | Households | 2023 |
| Little Italy (North East) Ltd. | Hospitality | 1996 |
| Little Rocket Records Limited | Information & communication | 2016 |
| Little Wren's Lettings Ltd | Real estate | 2023 |
| Live Entertainment & Arts Foundation | Education | 2023 |
| Lively UP Yourself Limited | Other services | 2020 |
| Living History (North East) Limited | Arts & recreation | 2003 |
| Livingstones Ministry Limited | Education | 2023 |
| Liyaghi Ltd | Hospitality | 2017 |
| Lizom Limited | Administrative & support | 2025 |