| 12 Hyde Park Limited | Real estate | 2004 |
| 12 John Clyne Ltd | Real estate | 2022 |
| 12 Jubilee Road Management Limited | Extraterritorial | 2010 |
| 12 Kelvin Grove Ltd | Households | 2007 |
| 12 Kendoa Road RTM Company Limited | Households | 2012 |
| 12 Kent House Road RTM Company Limited | Households | 2025 |
| 12 Kidbrooke Park Road Limited | Professional & scientific | 2010 |
| 12 Kildare Gardens Limited | Real estate | 1999 |
| 12 Kings Avenue (Management) Limited | Real estate | 1987 |
| 12 Kings Avenue Freehold Limited | Households | 2024 |
| 12 KWW Limited | Households | 2022 |
| 12 L.R. (Management) Limited | Real estate | 1995 |
| 12 Lambert Road Limited | Households | 1997 |
| 12 Lanhill Road Ltd | Real estate | 2023 |
| 12 Lauderdale Parade and 62 Castellain Road Limited | Real estate | 2019 |
| 12 Lennox Gardens Limited | Households | 2006 |
| 12 Lexham Gardens RTM Company Limited | Households | 2013 |
| 12 Limes Grove Limited | Households | 2001 |
| 12 Linden Gardens Limited | Households | 2021 |
| 12 Lindfield Gardens (Management) Ltd | Households | 1998 |
| 12 Lisgar Terrace Freehold Limited | Real estate | 2014 |
| 12 Lowfield Road Freehold Limited | Households | 2015 |
| 12 Lynn Road Limited | Households | 2004 |
| 12 Macs Close Limited | Real estate | 2017 |
| 12 Malvern Road Limited | Households | 2024 |
| 12 Management Group Ltd | Extraterritorial | 2019 |
| 12 Management Ltd | Professional & scientific | 2014 |
| 12 Manor Road W3 Freehold Limited | Extraterritorial | 2015 |
| 12 Margravine Gardens London Limited | Real estate | 2001 |
| 12 Maude Road (Camberwell) Limited | Households | 2020 |
| 12 Mildmay Grove South Freehold Limited | Households | 2017 |
| 12 Milespit Hill Freehold Limited | Households | 2012 |
| 12 Mill Lane RTM Limited | Real estate | 2012 |
| 12 Milton Road Freehold Company Limited | Real estate | 2006 |
| 12 Minden Road Freehold Limited | Households | 2024 |
| 12 MM Group Ltd | Hospitality | 2022 |
| 12 Montagu Square Ltd | Real estate | 2004 |
| 12 Moorgate Tenant Limited | Real estate | 2018 |
| 12 Moorhouse Road RTM Company Limited | Households | 2021 |
| 12 Moray Road N4 3LG Ltd | Households | 2024 |
| 12 Moreton Road CR2 Limited | Households | 2024 |
| 12 Morley Road RTM Company Limited | Households | 2017 |
| 12 Nelson's ROW Management Company Limited | Professional & scientific | 2003 |
| 12 Netherton Grove Limited | Real estate | 2020 |
| 12 Nevern Square (Management Company) Limited | Households | 2016 |
| 12 Nibthwaite Road Management Limited | Real estate | 2021 |
| 12 Northbrook Road Ltd | Real estate | 2025 |
| 12 Northwick Terrace Limited | Construction | 2003 |
| 12 Ormonde Gate Freehold Limited | Households | 2019 |
| 12 Ormonde Gate Leasehold Limited | Households | 2021 |
| 12 Ospringe Road (London) Limited | Real estate | 2001 |
| 12 Oxford Road Freehold Ltd | Administrative & support | 2016 |
| 12 Oxford Road Management Limited | Households | 1992 |
| 12 Park Hall Road Limited | Professional & scientific | 1991 |
| 12 Pear Breaks Freehold Limited | Households | 2019 |
| 12 Pembridge Square Management Company Limited | Real estate | 1999 |
| 12 Porchester Place Ltd | Hospitality | 2024 |
| 12 Porchester Square Ltd | Real estate | 2023 |
| 12 Powell Road Limited | Households | 2016 |
| 12 Priory Road Limited | Administrative & support | 2022 |
| 12 Q a Gate Ltd | Households | 2023 |
| 12 Queensberry Place Limited | Real estate | 2005 |
| 12 Radipole Road Limited | Households | 2010 |
| 12 Randolph Crescent Limited | Households | 1983 |
| 12 Rattray Road Freehold Limited | Households | 2025 |
| 12 Rays Limited | Information & communication | 2019 |
| 12 Redington Road Freehold Limited | Households | 2003 |
| 12 Richmond Road RTM Company Ltd | Households | 2016 |
| 12 Rivers Limited | Real estate | 2020 |
| 12 Rounds Boxing Ltd | Arts & recreation | 2013 |
| 12 Rounds Limited | Wholesale & retail | 2014 |
| 12 Rounds Management Limited | Administrative & support | 2024 |
| 12 RR Ltd | Real estate | 2024 |
| 12 Rutland Gate Limited | Households | 1983 |
| 12 Salisbury Road Property Management Limited | Households | 2010 |
| 12 Sarre Road Limited | Real estate | 2024 |
| 12 Schubert Road Management Company Limited | Households | 2005 |
| 12 Seasons Ltd | Professional & scientific | 2025 |
| 12 Services and Solutions Ltd | Information & communication | 2010 |
| 12 Seymour Road Limited | Extraterritorial | 2007 |
| 12 SGS Freehold Company Limited | Real estate | 2010 |
| 12 Sided Studios Ltd | Information & communication | 2024 |
| 12 Sloane Gardens Freehold Limited | Households | 2024 |
| 12 Smithfield General Partner Limited | Administrative & support | 2007 |
| 12 Smithfield Nominee NO.1 Limited | Extraterritorial | 2007 |
| 12 Smithfield Nominee NO.2 Limited | Extraterritorial | 2007 |
| 12 Smyrna Road Limited | Real estate | 2016 |
| 12 Southgate Ltd | Real estate | 2021 |
| 12 Spencer Hill (Wimbledon) Limited | Households | 1987 |
| 12 Square Consulting Ltd | Information & communication | 2020 |
| 12 ST Gabriels Road Limited | Households | 1992 |
| 12 ST Mark's Place (2) Limited | Households | 2001 |
| 12 Stafford Terrace Freehold Ltd | Households | 2021 |
| 12 Stanlake Road Limited | Real estate | 2001 |
| 12 Stoneyfields Ltd | Extraterritorial | 2021 |
| 12 Stowe Road Management Limited | Real estate | 2022 |
| 12 Strathmore Gardens Limited | Households | 1996 |
| 12 Streatham Common Residents Limited | Real estate | 1998 |
| 12 Tankerville Road Freehold Ltd | Real estate | 2020 |
| 12 Tanza Road Management Company Limited | Households | 1983 |