| Kestrel Property Holdings Limited | Real estate | 2017 |
| KEY2ID Limited | Information & communication | 2009 |
| Keycrown Properties Limited | Professional & scientific | 1993 |
| Keysight Technologies UK Limited | Administrative & support | 1999 |
| KH Mind Ltd | Health & social care | 2025 |
| Khader Associates Ltd | Health & social care | 2011 |
| Khyber Point Limited | Professional & scientific | 2025 |
| KI Electrical and Maintenance Ltd | Construction | 2025 |
| KI Media Ltd | Wholesale & retail | 2019 |
| Kick the Bricks Limited | Other services | 2023 |
| Kickham Construction Ltd | Construction | 2021 |
| Kiela Transport Services Limited | Transport & logistics | 2018 |
| Kielder Associates Ltd | Information & communication | 2011 |
| Kieran O'Donnell Limited | Professional & scientific | 2019 |
| Kiisu and Sebra Enterprises Limited | Information & communication | 2012 |
| KIK Payroll Solutions Limited | Professional & scientific | 2023 |
| Kikstart Limited | Professional & scientific | 2017 |
| Kilgour Technical Services Ltd | Construction | 2020 |
| Kiln Ride Management Company Limited | Households | 2009 |
| Kiln Ventures Limited | Professional & scientific | 2013 |
| Kimel Community Café CIC | Wholesale & retail | 2021 |
| Kimel Community CIC | Education | 2020 |
| Kimel Trading Ltd | Administrative & support | 2024 |
| KIND2U Living Limited | Health & social care | 2023 |
| Kindred Partners Ltd | Professional & scientific | 1996 |
| King Brothers Garage Services Ltd | Wholesale & retail | 2015 |
| King Fantasy Sports Ltd | Wholesale & retail | 2019 |
| King Retailer Limited | Wholesale & retail | 2023 |
| Kingfisher Enamelling Company Limited | Manufacturing | 1996 |
| Kingfisher Phoenix Finance Ltd | Professional & scientific | 2026 |
| Kingfisher Phoenix Ltd | Information & communication | 2022 |
| Kings Meadow Homes Reading Ltd | Construction | 2021 |
| Kings Quarter Management Company Limited | Households | 2010 |
| Kingsbury Consultants Limited | Manufacturing | 1995 |
| Kingshill Tree and Garden Services Ltd | Administrative & support | 2022 |
| Kingwood Limited | Hospitality | 2002 |
| Kipoili Properties Limited | Real estate | 2026 |
| Kiraavi Services Ltd | Information & communication | 2026 |
| Kiradvisory Limited | Financial services | 2015 |
| Kirbys BBQ Ltd | Other services | 2025 |
| Kirkby Accountants Ltd | Professional & scientific | 2012 |
| Kiss Engineering Limited | Professional & scientific | 2016 |
| Kitchen Fire Suppression Systems Ltd | Manufacturing | 2023 |
| Kite Studio Technologies Ltd | Wholesale & retail | 2025 |
| KJ & Sons Plumbing and Heating Ltd | Construction | 2019 |
| KJ Packaging Ltd | Wholesale & retail | 2024 |
| KJK Cars Ltd | Wholesale & retail | 2020 |
| Klarity AI Ltd | Information & communication | 2025 |
| KLG Drug Safety Ltd | Health & social care | 2014 |
| Knight IT Associates Limited | Information & communication | 2001 |
| Knight Structural Limited | Construction | 2021 |
| Knights CAD Services Ltd | Information & communication | 2016 |
| Knowledge Transfer and Design Ltd | Information & communication | 2024 |
| Known Consulting Ltd | Professional & scientific | 2025 |
| Knypersley Power Limited | Administrative & support | 2020 |
| KOB Financial Limited | Real estate | 2004 |
| KOI Studio Ltd | Manufacturing | 2025 |
| Koki Limited | Transport & logistics | 2015 |
| Koliko Films Limited | Information & communication | 2017 |
| Komba Group Ltd | Wholesale & retail | 2026 |
| Kombat Cards Ltd | Wholesale & retail | 2021 |
| Kong Racing Products & Services Ltd | Wholesale & retail | 2025 |
| Konvergent Holdings Limited | Financial services | 2020 |
| Konvergent Ltd | Information & communication | 2013 |
| Koosa Kids Limited | Health & social care | 2005 |
| Koush Property Limited | Other services | 2024 |
| Kowa Pharmaceutical Europe Co. Ltd. | Manufacturing | 2000 |
| KP Construction Ltd | Construction | 2021 |
| Kpmp Consultancy Ltd | Professional & scientific | 2025 |
| KPS Digital Ltd. | Administrative & support | 1997 |
| Krasimira Bodurova Locum Limited | Professional & scientific | 2015 |
| Kravia Limited | Professional & scientific | 2005 |
| Krisla Digital Solutions Limited | Information & communication | 2022 |
| Krlak IT Services Ltd | Information & communication | 2019 |
| Krlak Properties Ltd | Real estate | 2020 |
| Kroll Interiors (London) Ltd | Construction | 2022 |
| KRT Consulting Limited | Construction | 2005 |
| KS Film Productions UK Limited | Information & communication | 2025 |
| Ksgw Holdings Limited | Financial services | 2026 |
| KT Wells Limited | Professional & scientific | 2014 |
| Kubara Sound Mind Ltd | Health & social care | 2025 |
| Kuki Media LLP | | 2022 |
| Kushantha&Ayomie Property Management Limited | Administrative & support | 2025 |
| Kutaku Limited | Health & social care | 2023 |
| Kutchka Limited | Information & communication | 2001 |
| Kutchman Limited | Professional & scientific | 2014 |
| Kynisca Sports Management Limited | Financial services | 2024 |
| L & a Johal-Price Ltd | Wholesale & retail | 2025 |
| L & E Leadwork and Roofing Services Limited | Construction | 2021 |
| L J Wylder Sculpture Ltd | Arts & recreation | 2025 |
| L&D Living Limited | Real estate | 2021 |
| L&E Property Ltd | Real estate | 2019 |
| L&H Analytics Ltd | Professional & scientific | 2025 |
| L'Arte (Reading) Limited | Hospitality | 2023 |
| L.M. Van Moppes & Sons Limited | Wholesale & retail | 2005 |
| L2 Brands Ltd | Wholesale & retail | 2022 |
| LA Brands Ltd | Manufacturing | 2018 |
| LA Electrical Limited | Construction | 2000 |
| LAB Power Limited | Professional & scientific | 2015 |
| Labelservice Ltd | Information & communication | 2012 |