| Jones Sibs Ltd | Real estate | 2023 |
| Jordan Family Rentals Ltd | Hospitality | 2025 |
| Jorealestate Ltd | Real estate | 2019 |
| JP Pharma Consulting Ltd | Professional & scientific | 2023 |
| JWV Consultancy Services Limited | Professional & scientific | 2002 |
| K & L Houses Limited | Real estate | 2020 |
| K & S Foulkes Group Limited | Construction | 2024 |
| K. Ireland Kitchen Fitters Ltd | Construction | 2002 |
| Karadeniz Fast Food Ltd | Hospitality | 2024 |
| KE Solar Portfolio Limited | Financial services | 2015 |
| Kendley Limited | Manufacturing | 1997 |
| Kendrickproperty Limited | Construction | 2025 |
| Kervisia Ltd | Wholesale & retail | 2025 |
| Keystonewell Ltd | Administrative & support | 2026 |
| KIM Inspire | Health & social care | 2002 |
| KIM Inspire Social Enterprises Ltd | Hospitality | 2012 |
| Kingspan Energy Limited | Construction | 1978 |
| Kingspan Fastener Solutions Limited | Professional & scientific | 2023 |
| Kingspan Holdings (Insulation) Limited | Financial services | 1994 |
| Kingspan Investments Limited | Financial services | 2001 |
| Kingspan Light & Air Limited | Construction | 2013 |
| Kingspan Limited | Manufacturing | 1972 |
| Kingspan Services (UK) Limited | Financial services | 1998 |
| Kmac Property Sourcing Ltd | Real estate | 2021 |
| Knitmesh Technologies Limited | Manufacturing | 2017 |
| Komaia Ltd | Wholesale & retail | 2025 |
| KRM Precision Limited | Manufacturing | 2019 |
| KSP Europe Limited | Financial services | 2006 |
| Laburnum Drive Properties Limited | Real estate | 2025 |
| Lane Cove Care Limited | Health & social care | 2024 |
| Leevey Proofreading and Editing Limited | Manufacturing | 2022 |
| Leisure Estate Agents Ltd | Real estate | 2020 |
| Leverett Contracting Limited | Agriculture & fishing | 2003 |
| Liamscape Ltd | Extraterritorial | 2022 |
| Lilium Regale 100 Limited | Real estate | 2013 |
| LIN Acre Ltd | Hospitality | 2023 |
| Linham Limited | Wholesale & retail | 2021 |
| Little Mountain Outdoors Limited | Wholesale & retail | 2011 |
| Liverpool Bay Hotshop Ltd | Wholesale & retail | 2020 |
| Lixwm Garage Limited | Wholesale & retail | 2012 |
| LJ Accounting Services Limited | Professional & scientific | 2022 |
| LKJ Prescribing Ltd | Health & social care | 2025 |
| Llaethdy Mynydd Mostyn CYF | Manufacturing | 2021 |
| Llan DA Electrical Services Ltd | Construction | 2025 |
| Llys Y Gweilch Management Company Limited | Households | 2012 |
| Llys YR Efail Residents Ltd | Hospitality | 2002 |
| Lmaj Properties Limited | Real estate | 2021 |
| LMR Contracting Ltd | Construction | 2024 |
| Loan Resolutions UK Limited | Professional & scientific | 2008 |
| Local Estate Agent NW Ltd | Real estate | 2026 |
| Lodge Estate Agent Ltd | Real estate | 2020 |
| Lothbury Underwriting Limited | Financial services | 2004 |
| Lowri Consulting Ltd | Professional & scientific | 2014 |
| LPH Group Limited | Professional & scientific | 1995 |
| Lyons Paving and Landscaping Ltd | Administrative & support | 2023 |
| M a Adamson Properties Limited | Real estate | 2024 |
| M Higgs Limited | Professional & scientific | 2010 |
| M R Products Limited | Wholesale & retail | 2003 |
| M&R Evans Holdings Ltd | Financial services | 2025 |
| M&S Retail Enterprises Ltd | Wholesale & retail | 2025 |
| M.Klay Civils Limited | Administrative & support | 2025 |
| Maduzii Ltd | Wholesale & retail | 2022 |
| Maggie's Takeaway Limited | Hospitality | 2018 |
| Maggies Fish and Chips Ltd | Hospitality | 2025 |
| Mali & Penny Ltd | Wholesale & retail | 2024 |
| Manchester House (Llanfairfechan) Limited | Real estate | 2013 |
| Mane Lengths Limited | Other services | 2019 |
| Manorwall Estates Ltd | Agriculture & fishing | 2004 |
| MAP Cleaning Limited | Administrative & support | 2013 |
| Mapa Property Developments Ltd | Construction | 2025 |
| Mark Drinkwater Limited | Manufacturing | 2010 |
| Mark Strickland Consultancy Limited | Professional & scientific | 2015 |
| Mark Williams Toys & Gifts Limited | Manufacturing | 2006 |
| Market ME NOW Ltd | Information & communication | 2014 |
| Marmalade Holywell Ltd | Wholesale & retail | 2023 |
| Matelma Limited | Real estate | 2013 |
| Mavericks Motorcycles Limited | Wholesale & retail | 2015 |
| Mavericks R&D Limited | Financial services | 2019 |
| MAX Hafod Properties Ltd | Real estate | 2025 |
| MB Logistics (NW) Limited | Transport & logistics | 2014 |
| MB Technical Consulting Limited | Professional & scientific | 2017 |
| Mcgills Car and Commercial Limited | Wholesale & retail | 2008 |
| Mckinnel Developments Ltd | Construction | 2011 |
| Mclean Manufacturing Solutions Ltd | Manufacturing | 2024 |
| Mcminn Consulting Limited | Professional & scientific | 2024 |
| Memorial Care Limited | Health & social care | 2023 |
| Mental Mechanics Ltd | Professional & scientific | 2021 |
| Merseyside Streaming Ltd | Arts & recreation | 2002 |
| Metserv Consultancy and Engineering Services Limited | Professional & scientific | 2023 |
| MIA Enterprises Hub Limited | Financial services | 2024 |
| Micky Nickson Contractors Ltd | Construction | 2019 |
| Mike Joyce Caravan Repairs Limited | Manufacturing | 2014 |
| Mike Waite Nuclear Consulting Ltd | Professional & scientific | 2023 |
| Miller-Klein Associates Limited | Professional & scientific | 2001 |
| Millington Group Limited | Wholesale & retail | 2023 |
| Mini Machine Hire Ltd | Administrative & support | 2024 |
| Misty Waters Bar & Grill Ltd | Hospitality | 2021 |
| MLJ Properties Limited | Construction | 2018 |
| MM Auto Cars Ltd | Wholesale & retail | 2024 |
| Momentous Design Ltd | Professional & scientific | 2026 |