| Mike Denman Fitness Ltd | Other services | 2025 |
| Mike Worby Survey Consultancy Ltd | Construction | 2015 |
| Miles Better Roofing Ltd | Construction | 2025 |
| Milk Made Clothing Ltd | Wholesale & retail | 2021 |
| Millstone Stables Ltd | Arts & recreation | 2020 |
| Milo HR Limited | Administrative & support | 2023 |
| Milton Park Limited | Professional & scientific | 2007 |
| Mimii's Sauces & Foods LLP | | 2019 |
| Mineallmine Ltd | Hospitality | 2018 |
| MIR Cafe Limited | Hospitality | 2025 |
| Mirac Altinkaynak Ltd | Wholesale & retail | 2024 |
| Mirage Health Group Limited | Wholesale & retail | 2001 |
| MIX Music DJ (South Cambs) C.I.C. | Arts & recreation | 2024 |
| Miykui Limited | Wholesale & retail | 2024 |
| Mjkellystairs Ltd | Manufacturing | 2024 |
| Mjmp Services Limited | Real estate | 2015 |
| MJR Consultancy and Marketing Ltd | Professional & scientific | 2025 |
| MK Creative Ltd | Professional & scientific | 2018 |
| MKH Strategic Ltd | Professional & scientific | 2025 |
| Mkls Properties Ltd | Real estate | 2021 |
| MKR Services Ltd | Construction | 2020 |
| MLD Management Limited | Professional & scientific | 2020 |
| MLM Progress Ltd | Construction | 2019 |
| Mmae Engineering Ltd | Construction | 2022 |
| MMC Plumbing & Heating Limited | Construction | 2014 |
| Mn-Renovation Limited | Construction | 2024 |
| MOB Fires CIC | Health & social care | 2025 |
| Mock Interview Pro Ltd | Information & communication | 2024 |
| Mondeanos Ltd | Hospitality | 2025 |
| Monk's Walk School | Education | 2012 |
| Monk's Walk School Enterprises Limited | Hospitality | 2014 |
| Monkey DO Crew Limited | Construction | 2018 |
| Monkey DO Storage Limited | Transport & logistics | 2021 |
| Monkey SEE Property Limited | Real estate | 2022 |
| Monkey SEE Scenery Limited | Construction | 2016 |
| Mono Style Limited | Wholesale & retail | 2000 |
| Montoya Productions Ltd. | Arts & recreation | 2017 |
| Moorland House Clearances Limited | Transport & logistics | 2025 |
| Moreng Ltd | Professional & scientific | 2014 |
| Morgan Grounds Maintenance Ltd | Administrative & support | 2016 |
| MOT Your Car Ltd | Wholesale & retail | 2016 |
| Motorama Limited | Wholesale & retail | 2022 |
| Motorama Sales Limited | Wholesale & retail | 2021 |
| Moville Care Limited | Professional & scientific | 2007 |
| MP Nominees 1 Limited | Real estate | 2023 |
| MP Nominees Limited | Real estate | 2022 |
| MR Barrett Electrical Ltd | Construction | 2012 |
| MR Nowaz Tuition Ltd | Education | 2025 |
| MR SMF Saunders Limited | Health & social care | 2015 |
| MRE Empire Limited | Wholesale & retail | 2021 |
| MRM Media Limited | Other services | 2015 |
| MSA Engineering Limited | Transport & logistics | 2024 |
| MSC 2017 UK Ltd | Professional & scientific | 2017 |
| MSC Clinical UK Ltd | Professional & scientific | 2015 |
| MT92 Ltd | Wholesale & retail | 2025 |
| Mtge Partnership LLP | | 2020 |
| Muddy Boots Home Limited | Wholesale & retail | 2020 |
| Muddy Boots Sleepovers Franchise Limited | Other services | 2019 |
| Mueller Hale Consulting Ltd | Professional & scientific | 2021 |
| Muiz Fortune Management Limited | Administrative & support | 2015 |
| Mulberry Renovation Limited | Real estate | 2017 |
| Multiples Raise Healthcare Ltd | Health & social care | 2015 |
| Munro & Associates Advisory Limited | Professional & scientific | 2021 |
| Music Shack Ltd | Education | 2021 |
| Musicality Management Ltd | Arts & recreation | 2015 |
| Muum AI Ltd | Wholesale & retail | 2024 |
| MX Escapes Ltd | Administrative & support | 2026 |
| My Energy Consultants Limited | Professional & scientific | 2015 |
| My Welwyn Barbers Limited | Other services | 2020 |
| Mychurch Family Limited | Information & communication | 2018 |
| Myhomelikes Ltd | Households | 2023 |
| Mymenorasocks Limited | Wholesale & retail | 2024 |
| N & M Immigration Lawyers Ltd | Other services | 2023 |
| N S Ironton Builders and Decorators Limited | Administrative & support | 2009 |
| N&G RO Transport Ltd | Transport & logistics | 2025 |
| N18 Nutrition Ltd | Manufacturing | 2026 |
| Narayanswarup (UK) Limited | Wholesale & retail | 2015 |
| Natigo Ltd | Administrative & support | 2026 |
| National Social Care Training Limited | Other services | 2020 |
| National Stocktakers Limited | Professional & scientific | 2015 |
| Natureat Ltd | Hospitality | 2014 |
| Naut Trade Ltd | Wholesale & retail | 2023 |
| NBG Engineering Limited | Manufacturing | 2022 |
| NCS Countryside Services Limited | Administrative & support | 2014 |
| Neonlabs Consulting Ltd | Information & communication | 2017 |
| Netexpatise Limited | Information & communication | 2012 |
| New Tribe Properties Ltd | Real estate | 2024 |
| Newfieldmotors Ltd | Wholesale & retail | 2025 |
| Newmile Developments Limited | Real estate | 2014 |
| Next in Line Limited | Wholesale & retail | 1991 |
| NF Sports Massage Ltd | Health & social care | 2025 |
| NFH Europe Ltd | Professional & scientific | 2024 |
| NFT Tech Limited | Information & communication | 2021 |
| Nhomjewelry Ltd | Wholesale & retail | 2024 |
| Nick Morrison Rewards Ltd | Administrative & support | 2023 |
| Nickolds Maintenance Ltd | Other services | 2023 |
| Nickolds Properties Limited | Real estate | 2024 |
| Nieves Design Space Limited | Professional & scientific | 2020 |
| Night and Day Building Maintenance Ltd | Construction | 2011 |
| Niksen Legal Services Ltd | Professional & scientific | 2021 |