| JSK Estates Limited | Extraterritorial | 2007 |
| JSK Law Limited | Professional & scientific | 2005 |
| JSK Private Limited | Wholesale & retail | 2003 |
| JSM Advanced Limited | Health & social care | 2018 |
| JSW Sports Consultancy Limited | Arts & recreation | 2006 |
| JTC Couriers Ltd | Transport & logistics | 2007 |
| JTG Executive Support Services Limited | Administrative & support | 2016 |
| Judita Kuniskyte Photography Ltd | Information & communication | 2019 |
| Julie Holliday Hair Limited | Other services | 2006 |
| Juniper Way Holdings Ltd | Real estate | 2024 |
| Jupiter Star Properties Limited | Real estate | 2023 |
| JUS4 Ltd | Real estate | 2020 |
| Justcatering.Com Limited | Wholesale & retail | 2005 |
| Justmore Ltd | Hospitality | 2017 |
| Juttland Surveyors Limited | Construction | 2009 |
| JV Props Ltd | Arts & recreation | 2012 |
| JVL Accountancy Services Limited | Professional & scientific | 2003 |
| Jyoti Graphics & Typesetting Limited | | 1982 |
| K & P Greenford Supermarket Ltd | Wholesale & retail | 2007 |
| K & PS Ltd | Education | 2006 |
| K B Secure Solutions Ltd | Wholesale & retail | 2002 |
| K D Concepts Ltd | Wholesale & retail | 1994 |
| K D Construction Limited | Wholesale & retail | 1999 |
| K H Hillier Ltd | Arts & recreation | 2014 |
| K J D M S (Hemel) Limited | Real estate | 2004 |
| K J D M S (Tamworth) Limited | Real estate | 2004 |
| K&D Builders Ltd | Construction | 2021 |
| K. & F. Marketing and Consultancy Limited | Professional & scientific | 1987 |
| K. V. Transport & Logistics Ltd | Transport & logistics | 2024 |
| K. W. Props Limited | Information & communication | 2022 |
| K.C.Y. Limited | Real estate | 1999 |
| K.E. Investments Limited | Professional & scientific | 2003 |
| K.J. Discount Motor Spares Limited | Real estate | 1983 |
| K.K. Kerai & Sons (UK) Ltd | Construction | 2002 |
| K.M. Malak & Co Limited | Professional & scientific | 2004 |
| K4GNS Limited | Hospitality | 2025 |
| K8 Systems Limited | Information & communication | 2007 |
| Kafaalo Foundation Ltd | Other services | 2021 |
| Kailash Iifracombe Limited | Real estate | 2018 |
| Kalami Developments Limited | Real estate | 2001 |
| Kamal Electronics Limited | Construction | 1984 |
| Kamal Property Services Ltd | Real estate | 2020 |
| Kamax Associates Limited | Extraterritorial | 1998 |
| Kandel Holdings Limited | Financial services | 2025 |
| Kapital Interiors Ltd | Construction | 2018 |
| Kapproved Ltd | Administrative & support | 2022 |
| Karam Solutions Ltd | Real estate | 2023 |
| Karim Limited | Hospitality | 2002 |
| Karl Martins Ltd | Construction | 2004 |
| Kashkind Ltd | Financial services | 2019 |
| Kathryn Levitt Design Limited | Administrative & support | 2003 |
| Katrin Limited | Extraterritorial | 1991 |
| Katrin Properties Limited | Real estate | 2003 |
| Kavanah Builders Ltd | Construction | 2022 |
| Kavanah Consulting Services Ltd | Information & communication | 2019 |
| Kavanah Ltd | Construction | 2025 |
| Kavir (UK) Limited | Wholesale & retail | 2000 |
| Kavita Limited | Financial services | 1991 |
| Kaycalicious Cakes & Bakes Ltd | Hospitality | 2018 |
| Kaygisiz Properties Ltd | Real estate | 2015 |
| Kayman Enterprises Limited | Wholesale & retail | 2006 |
| KC Syndicate Ltd | Wholesale & retail | 2013 |
| Kcmb Properties Ltd | Real estate | 2001 |
| KCR Construction Ltd | Construction | 2021 |
| Keane's Transport Services Limited | Transport & logistics | 1996 |
| Keats Complementary Practice Ltd | Health & social care | 2000 |
| Keep London Moving Limited | Wholesale & retail | 2006 |
| Keith Charles. Folley | | 1999 |
| Kelco International Resources Limited | Professional & scientific | 1995 |
| Keld Limited | Real estate | 1997 |
| Kelly Hydraulics Limited | Construction | 2002 |
| Kelly Partners LLP | | 2008 |
| Keltik Limited | Professional & scientific | 1999 |
| Kelue Obiajula | | 1998 |
| Kelway Developments Limited | Construction | 2007 |
| Kema Enterprises | | 1997 |
| Kenilworth OIL Company Limited | Professional & scientific | 1933 |
| Kent & Co Limited | Professional & scientific | 2002 |
| Kenway Northwood Limited | Real estate | 1956 |
| Kerai Property Investments Limited | Real estate | 2004 |
| Kerdis Limited | Real estate | 1998 |
| Kevin Dalton Ltd | Transport & logistics | 2026 |
| Kevin James. Dutton | | 1999 |
| Kevin Reeds Limited | | 1994 |
| Kevin. Taiani | | 1998 |
| Kewal Property LLP | | 2023 |
| Key Factors First Limited | Administrative & support | 2003 |
| Key Notions Limited | Real estate | 1993 |
| Keybuild Limited | Professional & scientific | 1997 |
| Keyed-In Computers Limited | Information & communication | 1989 |
| Keyshia Limited | Health & social care | 2012 |
| Keystone Conservation & Construction Ltd | Construction | 2023 |
| Keytrust UK Limited | Other services | 2007 |
| KF Media Limited | Information & communication | 2007 |
| Khakh Investments Limited | Real estate | 2020 |
| Khalsa College London | Education | 1986 |
| Khalsa Transport Ltd | Transport & logistics | 2002 |
| Khetani Builders (UK) Limited | Construction | 2002 |
| KI Designs Limited | Professional & scientific | 1997 |
| Kian & Co. Limited | Professional & scientific | 2003 |