| Maggsea Marine Services Ltd | Fareham | 2024 |
| Magic Friends Ltd | Potters Bar | 2023 |
| Magic Heating Limited | Whitchurch | 2023 |
| Magic Pelagic Fishing Limited | Penzance | 2011 |
| Magic Shellfish Ltd | Driffield | 2013 |
| Magical Isle Limited | Isle Of Cumbrae | 2024 |
| Magical Wool Ltd | London | 2021 |
| Magicrop Limited | Beckenham | 2020 |
| Magna Rubrum Collis Limited | Rugeley | 2020 |
| Magnolia Bloodstock Limited | Newmarket | 2026 |
| Magnort (NI) Limited | Londonderry | 2021 |
| Magnuggit Livery CYF. | Ty Croes | 2024 |
| Magnus Environmental and Forestry Ltd | Whitehaven | 2016 |
| Magog Farm Limited | Cambridge | 1959 |
| Magrii Ltd | Scunthorpe | 2020 |
| Magwings Dogs Ltd | Preston | 2026 |
| MAH Bloodstock Ltd | Cambridge | 2022 |
| Mahsa Holdings Ltd | Edinburgh | 2026 |
| Maiden Estates Ltd | Perth | 2023 |
| Maidenhouse Limited | Grantham | 2013 |
| Maidenlands Tarn Ltd | Ulverston | 2017 |
| Maidfish Limited | London | 1981 |
| Maidstone Firewood Logs Ltd | Sittingbourne | 2025 |
| Maidstone Tree Services Ltd | Folkestone | 2016 |
| Mail Order Trees Ltd | Ely | 2025 |
| Maimai Limited | Aberdeen | 2008 |
| Main Agriculture and Plant Services Ltd | Billingshurst | 2024 |
| Main Garden Services Ltd | Alton | 2003 |
| Main Marine Limited | Hungerford | 2025 |
| Maine Coon Silver Paws Ltd | Doncaster | 2024 |
| Maines Farm Contracting Limited | Berwick-Upon-Tweed | 2012 |
| Maineview Farm Limited | Ballymena | 2024 |
| Mainline Growers Limited | Driffield | 2012 |
| Mains of Rhynie Limited | Leyland | 2018 |
| Mainstream Fisheries Limited | Lincolnshire | 2003 |
| Maipop Farm Limited | Wisbech | 2015 |
| Mair & Sons (Farmers) Limited | Cambs. | 1976 |
| Mair Farms Limited | Lincoln | 2012 |
| Maireannach Croft Ltd | Tighnabruaich | 2025 |
| Maison Barran Miles Ltd | London | 2021 |
| Maison Celine Puppy Limited | London | 2026 |
| Maison DES Animaux Ltd | Leicester | 2021 |
| Maison MMC Ltd | Greater London | 2025 |
| Maitland Bell Tree Services Limited | Totnes | 2013 |
| Maitland Farmers (Loop) Limited | Wellington | 2017 |
| Maitland Farms Limited | Aberdeenshire | 1994 |
| Maitland Fishing Limited | Aberdeen | 2002 |
| Majestic Services Incorporated Ltd | Church Stretton | 2023 |
| Majesticmainemajesty Ltd | Carlisle | 2025 |
| Major Dairy Farming Ltd | Devizes | 2022 |
| Major Farm Services Limited | Thame | 2014 |
| Major Farming Limited | Burton-On-Trent | 2014 |
| Major Trees Ltd | Exeter | 2005 |
| Majority World Food Limited | Corby | 2025 |
| Makaevo Kennels Ltd | Boston | 2022 |
| Makara Marine Aqua Ltd | Ruislip | 2023 |
| Make a Stand Limited | Gloucester | 2015 |
| Make the World Wild Ltd | York | 2020 |
| Makeit Dogs Limited | Harpenden | 2019 |
| Makepeace Forestry & Landscaping Limited | Hexham | 2023 |
| Makeupstore Ltd | Liverpool | 2020 |
| Makin Developments Wakefield Ltd | Leeds | 2014 |
| Making Light Work Limited | Leeds | 1997 |
| Makins Enterprises Ltd | Leeds | 2021 |
| Makins Fisheries Limited | Leicester | 2019 |
| Makins Soft Fruit Ltd | Leeds | 2014 |
| Makinson Farm Livery Stables Limited | Mill Lane, Aspull | 2000 |
| Makonza Sukutayi Holdings Limited | Norwich | 2022 |
| Maks Enterprise Limited | London | 2018 |
| MAL Leisure Limited | Wolverhampton | 2024 |
| Malaga International Horse Transport Limited | Leven | 2021 |
| Malawi Fruits | Glasgow | 2011 |
| Malawi Mania UK Ltd | Telford | 2020 |
| Malbro Farms Limited | Preston | 2012 |
| Malcolm Henry & Sons Farm Ltd | Cookstown | 2026 |
| Malcolm Jordan Limited | Ripley | 2009 |
| Malcolm M. Grant (Pitgrudy) | Nairn | 1961 |
| Malcolm Stewart Limited | Lockerbie | 2007 |
| Malcolm Wrisdale Limited | Spilspy | 1963 |
| Maldon Oyster Company Ltd. | Chelmsford | 2003 |
| Malehurst Farm Ltd | Shrewsbury | 2025 |
| Malerassa Ltd | Wisbech | 2021 |
| Malikinyota Ltd | Weston-Super-Mare | 2021 |
| Malkin Pest Control Ltd | Thatcham | 2023 |
| Mallabeny Farms Ltd | Clogher | 2021 |
| Mallaboy Farm Ltd | Ballymena | 2024 |
| Mallaig Divers Limited | Arisaig | 2015 |
| Mallaig Marine Ltd. | Mallaig | 2009 |
| Mallard Flyfishers Limited | Malmesbury | 2003 |
| Mallard Point Limited | Stamford | 2020 |
| Malleny Angling Ltd | Edinburgh | 2019 |
| Malleson Farming Limited | Gillingham | 2014 |
| Mallettea Ltd | Eye | 1997 |
| Mallory Park Fisheries Limited | Leicester | 1983 |
| Malmains Farm Limited | Dover | 2022 |
| Malmesbury Animal Sanctuary CIC | Swindon | 2022 |
| Malmswood Farm Limited | Harrow | 1993 |
| Malolo Ltd | Altrincham | 2015 |
| Malpass Services Ltd | Rugby | 2016 |
| Malshanger Farm | Berwick Upon Tweed | 1985 |