| MBS Analysis Limited | Information & communication | 2000 |
| Mccaig Services Limited | Information & communication | 2000 |
| Mcgregor's Signs Limited | Manufacturing | 1983 |
| Mckenzie Accountants Limited | Professional & scientific | 2006 |
| Mckinna Contracts Limited | Construction | 2003 |
| Mclaren Plastics Limited | Manufacturing | 1960 |
| Menzies Dougal (Nominees) Limited | Professional & scientific | 1995 |
| Menzies Dougal (Trustees) Limited | Professional & scientific | 1990 |
| Michael Laird Architects Limited | Professional & scientific | 2003 |
| Microclusters | | 2003 |
| Middleton Farms | | 1977 |
| Midlothian Advice & Resource Centre | Water & waste | 2004 |
| Midlothian Alignment Centre Limited | Transport & logistics | 2014 |
| Midlothian Community Action | Health & social care | 2001 |
| Midlothian Community Media Association | Information & communication | 2006 |
| Midlothian Financial Inclusion Network | Information & communication | 2005 |
| Mike Wray Limited | Financial services | 2002 |
| Milton Sheet Metal Works Limited | Construction | 1961 |
| MIT Retirement/Patron GP Limited | Financial services | 2001 |
| Mit/Patron GP Limited | Financial services | 2001 |
| Moray Estates Properties Limited | Agriculture & fishing | 1923 |
| Moray Place Limited | Real estate | 1987 |
| Morgan Grenfell Capital Limited Partnership | | 1989 |
| Morgan Grenfell Development Capital Limited Partnership | | 1990 |
| Motherly Indulgence Ltd | Wholesale & retail | 2026 |
| MRS Property Limited | Real estate | 2021 |
| Mungo Dunnett Associates Limited | Professional & scientific | 2002 |
| My Consultants Limited | Professional & scientific | 2002 |
| Nairn's Oatcakes Ltd. | Manufacturing | 1996 |
| Nettlingflat Farming Company | | 1987 |
| Nettlingflat Farming Company NO. 1 | | 2002 |
| Network ROI Ltd | Information & communication | 2006 |
| Newbattle Abbey College | Education | 2004 |
| Nial Stewart Developments Limited | Professional & scientific | 2000 |
| Northern Stars Corporation Limited | Financial services | 2001 |
| Northern Steeplejacks (Edinburgh) Limited | Administrative & support | 1986 |
| One SET UP Apparel Limited | Wholesale & retail | 2024 |
| Online-Cafe-Guide | | 2000 |
| Oracle Global Services Limited | Information & communication | 2003 |
| P & M Sinclair Limited | Construction | 2002 |
| P.D. Leisure Limited | Real estate | 1961 |
| Palace Properties Ltd. | Real estate | 1991 |
| Partners Group Management (Scotland) Limited | Professional & scientific | 2004 |
| Patron Capital Scotland GP Limited | Administrative & support | 2001 |
| Paul Cooper Computer Services Limited | Information & communication | 2000 |
| PBD Property Limited | Real estate | 2000 |
| Pendrich Height Services Limited | Administrative & support | 2003 |
| Penfriend Limited | Information & communication | 1999 |
| Pentland Press Limited | Manufacturing | 1986 |
| Pierino's Limited | Hospitality | 2006 |
| Pinocchio's Childrens Nurseries Limited | Health & social care | 2001 |
| Planning & Building Design Ltd. | Professional & scientific | 1998 |
| Port of Dundee Limited | Transport & logistics | 1995 |
| Porto & FI Ltd | Hospitality | 2005 |
| Potent 6 Limited | Professional & scientific | 2007 |
| Process Design and Engineering Limited | Professional & scientific | 1985 |
| Professional Money Management Ltd. | Financial services | 1997 |
| Prosper Management Services Limited | Professional & scientific | 2021 |
| Protective & Decorative Surface Coatings Ltd. | Construction | 1996 |
| Provenimus LLP | | 2006 |
| Public Image Communication Limited | Arts & recreation | 2003 |
| Pump Action Limited | Manufacturing | 1994 |
| PWP Marketing Design and Print | | 1991 |
| Quicktrace Limited | Information & communication | 2001 |
| R.S. Design Associates Limited | Professional & scientific | 1996 |
| Ramsay Moncrieff Interiors Ltd | Construction | 2022 |
| Rare Tea Company Limited | Hospitality | 2004 |
| Raymond Oliver Parcels Limited | Information & communication | 1965 |
| Raymond Wallace & Sons Limited | Other services | 1998 |
| RBS Special Opportunities Fund H LP | | 2007 |
| Relationships Scotland | Administrative & support | 2006 |
| Relax Property Investments Limited | Hospitality | 1997 |
| Remenham Properties Ltd. | Real estate | 2002 |
| Rettie & Company Trustee Limited | Real estate | 2003 |
| Revelator I.T. Limited | Information & communication | 2003 |
| Reynolds Enterprises Limited | Real estate | 2000 |
| Richard Murphy Architects Limited | Professional & scientific | 2003 |
| Robertson Property Development Limited | Real estate | 2000 |
| Robscot Limited | Professional & scientific | 2000 |
| RON Boyd Limited | Administrative & support | 1998 |
| Roslin Cell Sciences Limited | Professional & scientific | 2015 |
| Ross Farms and Company Limited | Agriculture & fishing | 1942 |
| Rosswynd Limited | Transport & logistics | 2002 |
| Rough Design Partnership Limited | Professional & scientific | 2002 |
| ROX Property Limited | Real estate | 2007 |
| Roxburgh Developments Ltd. | Construction | 2002 |
| RSC Management Limited | Hospitality | 1999 |
| SAC Corporate Trustee Limited | Financial services | 1994 |
| Salt 'N' Sauce Promotions Limited | Hospitality | 1997 |
| Sara Whitby Interiors Ltd | Other services | 1999 |
| SBS Publishing (Nt:Sport) Limited | Information & communication | 2004 |
| Scotland Yard Adventure Centre | Health & social care | 1986 |
| Scott Event Services Ltd. | Administrative & support | 2001 |
| Scottish Electrical Contractors Insurance Limited | Financial services | 1965 |
| Scottish Equitable (Managed Funds) Limited | Financial services | 1978 |
| Scottish Equitable Life Assurance Society | Professional & scientific | 1983 |
| Scovista Limited | Information & communication | 2008 |
| Second Afton Securities Limited | Real estate | 1975 |
| Sint Limited | Real estate | 1997 |
| Slimfreezeuk Limited | Other services | 2014 |