| Langstone Management Limited | Households | 1986 |
| Langton Aero Ltd | Administrative & support | 2024 |
| Language (Placement) Solution Limited | Education | 2014 |
| Lansdowne Place Limited | Real estate | 2002 |
| Laptronic Solutions Limited | Administrative & support | 2014 |
| Larchwood Management Company Ltd | Real estate | 2006 |
| Larcomes Financial Services Limited | Financial services | 1991 |
| Larcomes Legal Limited | Other services | 2019 |
| Larcomes LLP | | 2002 |
| Lark Project Services Ltd | Construction | 2022 |
| Larksmead Developments Limited | Construction | 2025 |
| Larksview Limited | Administrative & support | 2008 |
| Larry's Motors Ltd | Wholesale & retail | 2023 |
| Larrytrans Ltd | Transport & logistics | 2018 |
| LAS Rail Services Limited | Administrative & support | 2016 |
| Laser Estates Limited | Real estate | 2014 |
| Laser Light Cleaning Ltd | Administrative & support | 2025 |
| Laser Property Consultants Limited | Professional & scientific | 2023 |
| Laser Recharge Limited | Transport & logistics | 1990 |
| Laser Vision Limited | Health & social care | 2010 |
| Lasero Ltd | Real estate | 2018 |
| Lasmaventures Ltd | Real estate | 2026 |
| Latomus Holding Limited | Financial services | 2020 |
| Latomus Limited | Professional & scientific | 2020 |
| Latvian Community in Portsmouth CIC | Information & communication | 2024 |
| Laudum Properties Ltd | Construction | 2019 |
| Laughter Ltd | Information & communication | 2014 |
| Launchpad Creative Ltd | Information & communication | 2025 |
| Lau’S Consultancy Group (UK) Ltd | Professional & scientific | 2025 |
| Lavanta Cleaning Services Ltd | Administrative & support | 2021 |
| Lavender Moon Florist Ltd | Wholesale & retail | 2025 |
| Lawrence Mansions (Management) Limited | Hospitality | 2002 |
| Lawrence Warner Specialist Cars Limited | Wholesale & retail | 2010 |
| Lawson Estates Limited | Construction | 2005 |
| Lawson Rose Estate Agents Limited | Real estate | 2014 |
| Laxmar Limited | Administrative & support | 2019 |
| Laxmi Nilaiyam Limited | Real estate | 2023 |
| Layco Ltd | Financial services | 2022 |
| Lazerline Limited | Construction | 1998 |
| Lazyjacks Ltd | Hospitality | 2021 |
| LBK Car Sales Ltd | Wholesale & retail | 2021 |
| LBL Finishers Limited | Manufacturing | 1996 |
| LBL Limited | Professional & scientific | 1996 |
| LC Bloz Limited | Professional & scientific | 2025 |
| LC Construction & Management Solutions (Southern) Ltd | Construction | 2025 |
| LC Entertainment Limited | Professional & scientific | 2024 |
| LC Everything Limited | Arts & recreation | 2018 |
| LCA Autos Ltd | Wholesale & retail | 2026 |
| Lckrjc Ltd | Health & social care | 2014 |
| Lcmp Marketing Limited | Administrative & support | 2014 |
| Lcsu Limited | Professional & scientific | 2026 |
| LD Capital Investments Ltd | Financial services | 2026 |
| LDN Living Ltd | Construction | 2020 |
| LDP Roofing Limited | Construction | 2018 |
| Lead Engineering Ltd | Professional & scientific | 2020 |
| Lead Forensics Holdings Limited | Financial services | 2025 |
| Lead Forensics Limited | Information & communication | 2010 |
| Leadership Journeys Limited | Education | 2024 |
| Leading Solutions Holdings Limited | Financial services | 2025 |
| Leaf Life International Ltd | Health & social care | 2019 |
| Leal Construction Ltd | Real estate | 2019 |
| Leapforce Freight & Logistics Ltd | Wholesale & retail | 2026 |
| Learning Curves Personal Development Limited | Education | 1993 |
| Leasex Limited | Real estate | 2017 |
| Leaves Building & Maintenance Contractors Limited | Construction | 2009 |
| Ledamun Ltd | Administrative & support | 2010 |
| Ledborough Ltd | Real estate | 2023 |
| LEE Fancy Merchant Ltd | Wholesale & retail | 2025 |
| LEE Fletcher Funeral Services Limited | Other services | 2002 |
| Leeds Beds Ltd | Real estate | 2024 |
| Leena PVT Limited | Health & social care | 2015 |
| Leera Builders Ltd | Construction | 2015 |
| Lefay Engineering Limited | Manufacturing | 1972 |
| LEG8CY Ltd | Professional & scientific | 2023 |
| Legacy GLM Group Limited | Construction | 2021 |
| Legacy Landscapes Ltd | Administrative & support | 2017 |
| Legacyletterlife Limited | Professional & scientific | 2026 |
| Legatus Ltd | Information & communication | 2025 |
| Legend Engineering Ltd | Professional & scientific | 2025 |
| Leggacy Property Group Ltd | Real estate | 2017 |
| Legge & Co Holdings Limited | Financial services | 2025 |
| Legin Properties Limited | Real estate | 2006 |
| Legion Fitness Group Ltd | Other services | 2019 |
| Leicester Co-Packing Services Ltd | Professional & scientific | 2013 |
| Leigan Ltd | Real estate | 2023 |
| Leila's (South) Ltd | Hospitality | 2026 |
| Leinna Limited | Wholesale & retail | 2025 |
| LEJ Design Ltd | Professional & scientific | 2023 |
| Lema Asset Ltd | Real estate | 2022 |
| Lemafa Limited | Real estate | 2017 |
| Lemon Sky Photography Ltd | Information & communication | 2016 |
| Lennards Cafe Ltd | Hospitality | 2019 |
| Lennox House Limited | Hospitality | 2000 |
| Lennox Mansions (Southsea) Limited | Other services | 2016 |
| Leonard GTF Ltd | Real estate | 2026 |
| Leopard Tree Holdings Limited | Real estate | 2022 |
| LES Composites Ltd | Manufacturing | 2022 |
| LESSTAX2PAY (Portsmouth) Limited | Professional & scientific | 2011 |
| Let's DO Dinner Limited | Hospitality | 2011 |
| Leumas Logistics Ltd | Wholesale & retail | 2026 |