| MAS Farms Ltd | Kettering | 2004 |
| Mascott's Farm Ltd | Beverley | 2001 |
| Masdings ARB Solutions Ltd | Birmingham | 2026 |
| Mashfor Ltd | Manchester | 2015 |
| Maslok Ltd | Cheddar | 2015 |
| Mason Bro's Ltd | Sapcote | 2014 |
| Mason Farming | Driffield | 2010 |
| Mason Omoa Limited | Ayrshire | 1970 |
| Mason's Tree Contractors Limited | Abington | 2008 |
| Mass 110 Ltd | Reading | 2015 |
| Massa Horses UK Ltd | Charing | 2023 |
| Massereene Arable Farms Algeria Limited | Londonderry | 2020 |
| Massey Farmers (Garton) Limited | Driffield | 1975 |
| Massey Farms Ltd | Macclesfield | 2024 |
| Massive Corporation Limited | Coventry | 2011 |
| Masstock Arable (UK) Limited | Gloucestershire | 1989 |
| Mast-Scotland | Dunfermline | 2014 |
| Master Driers Limited | Bures | 1989 |
| Master Farm Services (G.B.) Limited | Bures | 1988 |
| Master Gardener Perenials Limited | Presteigne | 2026 |
| Masterbreeder Academy Limited | Belfast | 2021 |
| Masterbreeder Limited | Belfast | 2022 |
| Masterclass Developments Limited | Heathfield | 2000 |
| Masterfish Ltd. | Whitstable | 2011 |
| Masterfountain Limited | Haverfordwest | 2000 |
| Mastergen Ltd | Taunton | 2014 |
| Masters & Company Limited | Dunmow | 1926 |
| Masters Construction Poole Ltd | Knottingley | 2013 |
| Masters Spreading Limited | Goole | 2017 |
| Masterseries Holdings Limited | Belfast | 2019 |
| Masterton Property Services Ltd | Kirknewton | 2025 |
| MAT Stubbs Contracting Ltd | Louth | 2014 |
| Mat-Ewes Ltd | Tavistock | 2024 |
| Matahorn Ltd | Newmarket | 2019 |
| Matariki Limited | Dumfries | 2025 |
| Matea Sea Ltd | Egham | 2022 |
| Materia Earth Ltd | London | 2021 |
| Materra Ltd | London | 2019 |
| Matford Farm Limited | Lymington | 2018 |
| Mather & SON Farms Limited | Herne Bay | 2024 |
| Matherpropertylandscape Ltd | Macclesfield | 2020 |
| Matheson's Ltd. | Elgin | 2006 |
| Mathieson Trees Ltd | Dingwall | 2025 |
| Mathison Registered Farriers Limited | Hull | 2007 |
| Matinley Farms Ltd | Selkirk | 2003 |
| Matley Honey Co Ltd | Hyde | 2025 |
| Matlock Wines Limited | Matlock | 2023 |
| Matrix Crop Care Ltd | London | 2018 |
| Matrixglen Gundogs Ltd | Thornhill | 2022 |
| Matson Farms Limited | Cumbria | 1974 |
| Matsya Technologies Ltd | Sheffield | 2021 |
| Matt Bayles Professional Tree Care Ltd | Newton Abbot | 2007 |
| Matt Crawley Racing Ltd | Newmarket | 2023 |
| Matt Crompton Farrier Services Ltd | Rugeley | 2026 |
| Matt Dairies Ltd | Fivemiletown | 2013 |
| Matt Endeavours Limited | Ipswich | 2017 |
| Matt Hale Tree Surgery Ltd | Gloucester | 2014 |
| Matt Howard Services Limited | Sittingbourne | 2016 |
| Matt Leech Treecare Ltd | Farnham | 2022 |
| Matt Mole Fishing Limited | Manchester | 2018 |
| Matt Rogers Farming Limited | Plymouth | 2020 |
| Matt Sellars Tree Surgeon Limited | Leeds | 2012 |
| Matterley Farming | Winchester | 2017 |
| Matthew Bond Enterprises Limited | Tamworth | 2011 |
| Matthew DM Lewis Ltd | Cwmbran | 2023 |
| Matthew Gregory King Limited | Northwich | 2004 |
| Matthew Hustler Limited | Norwich | 2018 |
| Matthew Leece Limited | Preston | 2004 |
| Matthew Murray Tree Services Ltd | Stockport | 2021 |
| Matthew Staples Dwcf Limited | Dorking | 2003 |
| Matthew Tucker Ltd | Wick | 2025 |
| Matthew West Ltd | Fraserburgh | 2024 |
| Matthew's Plants Ltd | Harlow | 2022 |
| Matthews Bros. Limited | St. Austell | 2010 |
| Matthews Flower Growers Company Ltd | Salisbury | 2014 |
| Matthews Garden Maintenance Ltd | London | 2023 |
| Matthews Plant (Cornwall) Limited | Wadebridge | 1998 |
| Matthews Shellfish Limited | Par | 2006 |
| Matthews' Aquatic Paradise Ltd | Bury St. Edmunds | 2024 |
| Mattioli Fishings Ltd | Loughborough | 2025 |
| Matts Farriery Limited | Bicester | 2025 |
| Maurice Crouch (Growers) Limited | Wisbech | 1944 |
| Maurice Flower & SON Limited | Salisbury | 1958 |
| Maurice Mandry Limited | Chertsey | 1947 |
| Maurice Mason Limited | Kings Lynn | 1947 |
| Maurice Wilson (Farming) Limited | Near Pontefract | 1960 |
| Mautby Farms Limited | Great Yarmouth | 1960 |
| Mauve (Eco) Ltd | Derby | 2021 |
| Mauvetramp Limited | Edinburgh | 1996 |
| Maverick (Weymouth) Limited | Weymouth | 1996 |
| Maviga Europe Limited | London | 1997 |
| Mavis Park Holdings Limited | Peterhead | 2021 |
| Mavitty Agri Limited | Omagh | 2014 |
| Mavush Ltd | Buckingham | 2023 |
| MAW Holdings Limited | Goole | 1991 |
| Mawdsley Bros. Farms Limited | Ormskirk | 1999 |
| Mawmill Produce Limited | Kinross | 2025 |
| Mawthorpe Farms Limited | Lincolnshire | 1954 |
| MAX Dunford Farming Limited | Penrith | 2023 |
| MAX Routledge Ltd. | Godalming | 2016 |