| Lhob Ltd | Other services | 2023 |
| Libanus Lifestyle (Wales) C.I.C. | Administrative & support | 2015 |
| Liberty Care Limited | Health & social care | 2005 |
| Libics Gastech Limited | Construction | 2022 |
| Libics Improvements Ltd | Construction | 2020 |
| Lila Food & Pastry Limited | Hospitality | 2019 |
| Lillieum Ltd | Other services | 2013 |
| Lindt Education Limited | Education | 2017 |
| Linhope International (UK) Limited | Professional & scientific | 2019 |
| Little Einsteins Academy Ltd | Health & social care | 2014 |
| Little Mill Catering Services Ltd | Hospitality | 2018 |
| Little Orchard CBD Ltd | Health & social care | 2023 |
| Little Unicorns Daycare Ltd | Health & social care | 2019 |
| Live & Direct Utilities Limited | Construction | 2024 |
| Livegood Properties Limited | Real estate | 2024 |
| LJF Windows Ltd | Construction | 2024 |
| Llew Bach Co Ltd | Wholesale & retail | 2024 |
| Lloyd IT Limited | Information & communication | 2025 |
| Loading Maintenance Services Limited | Manufacturing | 2012 |
| LOX by Leane Ltd | Other services | 2026 |
| LP Carpentry Ltd | Manufacturing | 2019 |
| LR Solutions Limited | Information & communication | 2022 |
| LT Plumbing & Heating Services Ltd | Construction | 2025 |
| Luke Briggs Building & Roofing Contractor Limited | Construction | 2020 |
| LUX Motos Studios Ltd | Information & communication | 2026 |
| Luxel Solutions Ltd | Manufacturing | 2011 |
| LV Plant Ltd | Construction | 2026 |
| M & D Land Solutions Limited | Water & waste | 2023 |
| M E Superior GAS Services Limited | Other services | 2017 |
| M H Development Services Limited | Wholesale & retail | 2010 |
| M J & Family Holdings Ltd | Hospitality | 2024 |
| M J Letting Ltd | Real estate | 2019 |
| M&L Property Developments (South Wales) Ltd | Construction | 2023 |
| M&P Property Group Ltd | Real estate | 2020 |
| M&P Property Management (Newport) Ltd | Real estate | 2020 |
| Macan Engineering Limited | Manufacturing | 2005 |
| Made YOU Look Events Limited | Professional & scientific | 2025 |
| MAE & Co Consultancy Ltd | Professional & scientific | 2024 |
| Main Quality Engineering Limited | Construction | 2011 |
| Mainwaring Properties Ltd | Real estate | 2025 |
| Makeup Locker Limited | Other services | 2020 |
| MAL Heating and Plumbing Limited | Construction | 2024 |
| Marc Jones Logistics Ltd | Transport & logistics | 2024 |
| Margail Investments Ltd | Real estate | 2024 |
| Market Place Caffi Limited | Hospitality | 2015 |
| Markham Playgroup Limited | Education | 2013 |
| Marmaris 17 Limited | Professional & scientific | 2017 |
| Masonry and Construction Limited | Construction | 2021 |
| Maternityhaven Limited | Wholesale & retail | 2024 |
| Mathern Limited | Professional & scientific | 2014 |
| Matthew Jones Ceramics Barry Ltd | Manufacturing | 2020 |
| Mayberry Pharmacy Limited | Health & social care | 1999 |
| Mayprop Limited | Real estate | 2012 |
| MC Marketing Consultancy Ltd | Other services | 2015 |
| Mckenzies Lettings Limited | Households | 2026 |
| MDR Heating Services Ltd | Construction | 2021 |
| Meadowgate Residents Management Limited | Real estate | 2023 |
| MEB Property Management Ltd | Real estate | 2022 |
| Memsafe Limited | Other services | 2003 |
| MEOW1718 Limited | Hospitality | 2026 |
| Mercavo Ltd | Wholesale & retail | 2026 |
| MG125 Limited | Hospitality | 2026 |
| Mhends CIC | Arts & recreation | 2025 |
| Micahjproperties Ltd | Construction | 2025 |
| Mighty Oaks Blackwood Ltd | Health & social care | 2023 |
| Mike Needles Limited | Other services | 2018 |
| Millbrook Care Home Limited | Health & social care | 2013 |
| Millers Engineering Ltd | Manufacturing | 2025 |
| Miracle Van Hire Limited | Administrative & support | 2014 |
| MJP Power Ltd | Construction | 2026 |
| MKL Rental Properties Ltd | Real estate | 2024 |
| Mo's Top Style Barber Ltd | Other services | 2024 |
| Mocha Travel Ltd | Transport & logistics | 2026 |
| Monico Property Development Ltd | Construction | 2025 |
| Monkeyboy Enterprises Ltd | Wholesale & retail | 2018 |
| Monometro Limited | Transport & logistics | 1997 |
| Monroe's Aesthetics & Wellness Clinic Ltd | Other services | 2024 |
| Monte Kifto Limited | Construction | 2024 |
| Moonbolt Enterprises Ltd | Information & communication | 2024 |
| Morgan Opulent Real Estate Limited | Hospitality | 2025 |
| Morgrun Ltd | Real estate | 2019 |
| Morkins Limited | Real estate | 2025 |
| Moses Garden Maintenance Ltd | Administrative & support | 2024 |
| MOTION29 Limited | Manufacturing | 2006 |
| Motorfix Blackwood Ltd | Wholesale & retail | 2025 |
| Mountain Property Group Ltd | Construction | 2023 |
| Mountjoy Enterprises Limited | Administrative & support | 2016 |
| Mpaf Limited | Construction | 2006 |
| MR Eight Fish & Chip Shop Ltd | Hospitality | 2026 |
| MSP Plumbing, Heating & Property Maintenance Ltd | Construction | 2010 |
| Multicrete Ltd | Construction | 2025 |
| Muqas Trade Ltd | Wholesale & retail | 2024 |
| Murray’S Plumbing & Heating Services Ltd | Construction | 2026 |
| Musashi Auto Parts UK Limited | Real estate | 1993 |
| MVB Rigging Ltd | Arts & recreation | 2025 |
| N&P Property Solutions Ltd | Real estate | 2019 |
| N&R & Sons Ltd | Real estate | 2025 |
| Naanaghai Ltd | Wholesale & retail | 2021 |
| Nails by Livvie Ltd | Other services | 2025 |
| Nails by Philippa Ltd | Other services | 2022 |