| Holy COW (UK) Productions Ltd | Arts & recreation | 2010 |
| Home Inspections Limited | Professional & scientific | 2026 |
| Homehelpwatford Ltd | Health & social care | 2019 |
| Homora Ltd | Wholesale & retail | 2025 |
| Hoskote Limited | Health & social care | 2022 |
| House of Shika Catering Ltd | Hospitality | 2026 |
| HRM Contracts Limited | Construction | 2018 |
| HRM Green Trading AS Revival ST Albans Limited | Construction | 2025 |
| Hydrate Group Limited | Professional & scientific | 2017 |
| Hydro-Ready Limited | Energy | 2025 |
| ICV Building Services Ltd | Construction | 2020 |
| IDC Roofing and Leadwork Specialists Limited | Construction | 2022 |
| Idyllic Tutor Ltd | Wholesale & retail | 2026 |
| Imajinn Limited | Information & communication | 2001 |
| Imperial & Grill Limited | Hospitality | 2025 |
| Indo Chinese Foods Ltd | Hospitality | 2025 |
| Infinity Clean Energy Ltd | Construction | 2025 |
| Infomatrix Consultants Limited | Wholesale & retail | 2015 |
| INK and Laser Ltd | Education | 2026 |
| Innovare Properties Limited | Real estate | 2020 |
| Inside OUT Brand YOU Ltd | Professional & scientific | 2022 |
| Insync Property Investments Ltd | Real estate | 2022 |
| Insync Property Management Ltd | Real estate | 2016 |
| Interiors by Teco Ltd | Professional & scientific | 2025 |
| Ionel & LIA Property Limited | Real estate | 2024 |
| IT Systems Service Ltd | Information & communication | 2011 |
| J & a Strategic Investment Limited | Information & communication | 2025 |
| J K N a Training Limited | Education | 2005 |
| J3TZINE Ltd | Information & communication | 2023 |
| Jack the Rigger Limited | Information & communication | 2017 |
| JACK2MAX Consultancy Limited | Professional & scientific | 2018 |
| Janet Stillman Consultancy Limited | Administrative & support | 2017 |
| Jawstock Limited | Construction | 2023 |
| JC Performance Ltd | Arts & recreation | 2024 |
| JC Plastering Services Ltd | Construction | 2025 |
| Jender Homes Limited | Construction | 2020 |
| JET Plus Cleaning Services Ltd | Administrative & support | 2025 |
| Jett Ltd | Wholesale & retail | 2025 |
| JIE Search Ltd | Administrative & support | 2015 |
| JLI Services Limited | Arts & recreation | 2021 |
| JM Henry Investments Ltd | Financial services | 2025 |
| JM Prime Technologies Limited | Information & communication | 2012 |
| Jmptyresuk Limited | Wholesale & retail | 2024 |
| JO 1ANNEVALEN Company Ltd | Health & social care | 2021 |
| JSJ Civils Ltd | Construction | 2024 |
| K.J.Sumption Ltd | Professional & scientific | 2020 |
| Kamdur Limited | Information & communication | 2023 |
| Karen Murphy Coaching Ltd | Education | 2025 |
| Katherine Foley Recruitment Ltd | Administrative & support | 2026 |
| KC Flooring Specialists Limited | Construction | 2018 |
| Keshav Foods Limited | Wholesale & retail | 2025 |
| Key Link Solutions Ltd | Information & communication | 2026 |
| Kimbo Investment Property Limited | Real estate | 2021 |
| Kind Studio Ltd | Arts & recreation | 2015 |
| Kingdom Earthworks & Remediation Ltd | Construction | 2025 |
| Kinstead Financial Ltd | Financial services | 2026 |
| Kirik Makas Ltd | Other services | 2019 |
| Kottu King Ltd | Hospitality | 2022 |
| KR5 Properties Ltd | Real estate | 2024 |
| Kripx Ltd | Financial services | 2025 |
| KTR Rigging Ltd Limited | Construction | 2025 |
| LA Webster Renovation Ltd | Construction | 2025 |
| Ladysmith Road Management Limited | Hospitality | 1999 |
| Langley Car & Commercial Limited | Professional & scientific | 2014 |
| Lawes Consultancy Limited | Information & communication | 2026 |
| LCS GAS and Heating Services Ltd | Construction | 2018 |
| LCS Property Services Watford Ltd | Construction | 2013 |
| LDP Print Limited | Manufacturing | 2021 |
| Leavesden Investments Limited | Financial services | 2013 |
| Lever London Limited | Wholesale & retail | 2024 |
| LG Tier One Solutions Limited | Professional & scientific | 2025 |
| Lifesector Property Management Limited | Professional & scientific | 1989 |
| Lime Electrical Services Ltd | Construction | 2025 |
| Limitless Rides Ltd | Transport & logistics | 2026 |
| Lincoln Global Multi Services Ltd | Transport & logistics | 2025 |
| Lingo Legends Ltd | Education | 2019 |
| Lisa Mccallum Travel Consultancy Limited | Administrative & support | 2016 |
| Little Cassiobury Community Interest Company | Extraterritorial | 2013 |
| Little Heath Farm Nursery Ltd | Agriculture & fishing | 2019 |
| Livewired Electrical Services Ltd | Construction | 2023 |
| Lloyd's Hospitality Consultancy Ltd | Transport & logistics | 2020 |
| LNS (Bedmond) Limited | Financial services | 2007 |
| London Waterproofing Solutions Limited | Construction | 2014 |
| LSB Fireplaces Ltd | Construction | 2022 |
| Lucy’S Little Patisserie Ltd | Wholesale & retail | 2022 |
| LWS Projects Ltd | Construction | 2018 |
| M & B Financial Ltd | Financial services | 2022 |
| M&C Specialist Motors Ltd | Wholesale & retail | 2021 |
| MAC Contract Services Limited | Administrative & support | 2015 |
| Madells Builders Ltd | Construction | 2024 |
| Madiba Allure Limited | Wholesale & retail | 2024 |
| Malde Engineering Services Limited | Administrative & support | 2007 |
| Mamiloo Estates Ltd | Real estate | 2025 |
| MAP Consultancy Services Limited | Financial services | 2024 |
| Mark Sheridan Ltd | Professional & scientific | 2020 |
| Mattco UK Limited | Wholesale & retail | 2009 |
| Matterhorn Property Investments Ltd | Real estate | 2020 |
| Mcres Consultancy Limited | Professional & scientific | 2022 |
| Melwood Training Ltd | Professional & scientific | 2019 |
| Merap Ltd | Construction | 2019 |