| 39 Belsize Square Limited | Real estate | 1972 |
| 39 Peaks Limited | Professional & scientific | 2010 |
| 3ALPHA Consulting Ltd | Administrative & support | 2017 |
| 3D Design & Planning Ltd | Professional & scientific | 2019 |
| 3D Harvest Ltd | Agriculture & fishing | 2021 |
| 3D International Group LLP | | 2023 |
| 3DEES Transport Services Limited | Transport & logistics | 2012 |
| 3ED Limited | Health & social care | 2017 |
| 3ILM Wireless Limited | Professional & scientific | 2019 |
| 3M Electrical Ltd | Energy | 2022 |
| 3MN Ltd | Professional & scientific | 2024 |
| 3P Ventures Limited | Real estate | 2019 |
| 3PA-CONSULTING Ltd | Information & communication | 2009 |
| 3R Partners (Investments) Limited | Professional & scientific | 2013 |
| 3ROSES Spa Ltd | Other services | 2023 |
| 3Z Capital Ltd | Real estate | 2019 |
| 3ZEE Consulting Limited | Professional & scientific | 2023 |
| 4 Brackenbury Gardens Freehold Limited | Households | 2022 |
| 4 Cast Systems Limited | Professional & scientific | 2014 |
| 4 E'S Facilitation Limited | Professional & scientific | 2021 |
| 4 Infinity Limited | Real estate | 2022 |
| 4 Lyndhurst Road Limited | Households | 1993 |
| 4-6 Sloane Gardens RTM Company Limited | Households | 2010 |
| 40 Redcliffe Gardens Limited | Real estate | 2008 |
| 40-46 Leaford Crescent Freehold Company Limited | Households | 2019 |
| 41 NG Limited | Real estate | 1999 |
| 42 BPG Limited | Households | 2004 |
| 42 Kingsfield Road Limited | Households | 1992 |
| 420 Investments Limited | Financial services | 2024 |
| 43 Draycott Place Limited | Households | 2004 |
| 43 High Street Freehold Management Limited | Households | 2024 |
| 43-45 Brondesbury Road Limited | Households | 2006 |
| 44 Belsize Avenue Limited | Real estate | 1997 |
| 44 Blomfield Road Limited | Households | 1983 |
| 44 Chapel Park Road, ST Leonards on Sea Limited | Real estate | 2006 |
| 44 Oxford Road Limited | Extraterritorial | 2015 |
| 444 Dental Ltd | Health & social care | 2020 |
| 45 Christchurch Hill and 28 Well Walk Freehold Limited | Households | 2018 |
| 45 Rickmansworth Road (Freehold) Limited | Households | 1999 |
| 456 Founder Limited Partnership | | 2019 |
| 46 Bacon Street LLP | | 2020 |
| 46 Phillin Limited | Health & social care | 2007 |
| 47 Sutherland Residents Limited | Real estate | 1980 |
| 48 Barry Road Management Limited | Households | 1995 |
| 49-50 Kendal Street Limited | Real estate | 2012 |
| 4A Merle Property Services Ltd | Construction | 2026 |
| 4C Infoengg Ltd | Information & communication | 2016 |
| 4D Tech Consulting Ltd | Information & communication | 2023 |
| 4DOG Productions Ltd | Information & communication | 2016 |
| 4ERP Ltd | Information & communication | 2022 |
| 4HEARTS Limited | Real estate | 2019 |
| 4MD Devco 1 Limited | Construction | 2026 |
| 4RYECROFT Management Company Limited | Households | 2014 |
| 5 Agile Ltd | Information & communication | 2014 |
| 5 Cobham Terrace RTM Company Limited | Households | 2009 |
| 5 Fellows Road Residents Association Limited | Real estate | 1984 |
| 5 Gladstone Road RTM Company Limited | Households | 2026 |
| 5 NET Capital Ltd | Real estate | 2021 |
| 5 NET Credit Opportunities Ltd | Financial services | 2023 |
| 5 Star AFG Ltd | Real estate | 2024 |
| 5 Star Desk Ltd | Manufacturing | 2024 |
| 5 Upper Park Road Management Company Limited | Real estate | 2000 |
| 5-11 Cheyne Gardens RTM Company Limited | Households | 2010 |
| 50 Elsworthy Road Limited | Households | 1996 |
| 506 Productions Ltd | Information & communication | 2021 |
| 51 Belsize Avenue NW3 Freehold Limited | Households | 2012 |
| 51 Belsize Park (Freehold) Limited | Real estate | 2003 |
| 51 Belsize Park Gardens Limited | Administrative & support | 2000 |
| 51 Victoria Road Ltd | Real estate | 2020 |
| 51, Belsize Avenue NW3 Limited | Households | 1976 |
| 517 Homes Ltd | Real estate | 2023 |
| 52-61 Byewaters Management Limited | Real estate | 2003 |
| 55 Elgin Crescent Limited | Real estate | 1998 |
| 57 Balcombe Street Limited | Real estate | 1999 |
| 57 Melrose Avenue Ltd | Real estate | 2022 |
| 58 Kempe Road Ltd | Real estate | 2023 |
| 5ELEMENTS Ltd. | Information & communication | 2024 |
| 5Y Solutions Ltd | Health & social care | 2021 |
| 6 Castellain Road Limited | Real estate | 1983 |
| 6 Cats Norway Limited | Professional & scientific | 2016 |
| 6 Lyndhurst Gardens Limited | Real estate | 1981 |
| 6 Netherford Road Limited | Construction | 2007 |
| 60 Brompton Road Management Company Limited | Administrative & support | 2006 |
| 60 Penyston Management Limited | Households | 1991 |
| 607 IT Solutions Ltd | Information & communication | 2024 |
| 60FITNESS Ltd | Other services | 2024 |
| 61 - 84 DE Bohun Avenue Management Co. Limited | Real estate | 1984 |
| 61 Greencroft Gardens (Management) Limited | Real estate | 1986 |
| 62 Belsize Park Gardens Co. Ltd | Households | 2017 |
| 63 Redington Road Limited | Real estate | 1994 |
| 63 Selhurst Road Limited | Hospitality | 1999 |
| 64 Edgware Road Limited | Other services | 2018 |
| 65 Cadogan Square RTM Company Limited | Households | 2020 |
| 65PINERD Ltd | Households | 2019 |
| 66 Capital Ltd | Financial services | 2020 |
| 66 Graham Road Management Limited | Households | 2024 |
| 67 Cornwall Gardens Limited | Households | 1980 |
| 6CATS Group Ltd | Professional & scientific | 2016 |
| 6CATS Pro Ltd | Professional & scientific | 2020 |
| 6CATS UK Services Ltd | Financial services | 2018 |