| Krys Consulting Ltd | Professional & scientific | 2024 |
| Krystal Security Services Ltd | Administrative & support | 2019 |
| Krytical Solutions Limited | Professional & scientific | 2015 |
| KS Beginnings Limited | Professional & scientific | 2010 |
| KS Corporation Ltd | Wholesale & retail | 2025 |
| KS Group Consulting Limited | Information & communication | 2016 |
| Ks&A Security Solutions Ltd | Administrative & support | 2026 |
| Ks&H Homes Ltd | Real estate | 2024 |
| Ksah Trading Ltd | Wholesale & retail | 2022 |
| KSB Electrical Instalation Ltd | Construction | 2025 |
| KSB Retail Limited | Wholesale & retail | 2018 |
| Ksja Ltd | Real estate | 2025 |
| KSP Pharma Ltd | Wholesale & retail | 2023 |
| Ksquare Beauty & Spa Ltd | Other services | 2018 |
| KSR Dynamics Ltd | Wholesale & retail | 2024 |
| KSS Accretion Limited | Real estate | 2023 |
| KSV Property Services Limited | Construction | 2022 |
| KT Couture Ltd | Administrative & support | 2023 |
| KT Motors Trading Ltd | Manufacturing | 2007 |
| Ktfranklin Ltd | Information & communication | 2025 |
| KTH Group Ltd | Real estate | 2019 |
| KTL Coaches Limited | Transport & logistics | 2017 |
| KTP Investments Limited | Other services | 2013 |
| KU Circle LLP | | 2023 |
| Kube IT Resources Ltd | Information & communication | 2021 |
| Kubera Associates Limited | Real estate | 2017 |
| Kudrati Limited | Wholesale & retail | 2005 |
| Kudu Holdings Ltd | Financial services | 2015 |
| Kuhn Upholstery Limited | Other services | 2022 |
| Kukla Electrical Services Limited | Construction | 2007 |
| Kultralab Ltd | Information & communication | 2019 |
| Kumari Couture Limited | Wholesale & retail | 2025 |
| KUN and JAR Mahal Ltd | Professional & scientific | 2025 |
| Kundy Treasures Limited | Health & social care | 2014 |
| Kuromatsu Ltd | Information & communication | 2011 |
| Kurt Shannon Services Ltd | Construction | 2020 |
| KUS Outcomes Ltd | Health & social care | 2013 |
| Kuvashpa Holding Ltd | Real estate | 2024 |
| Kuvashpa Ltd | Professional & scientific | 2021 |
| KV Beauty & Spa Limited | Other services | 2026 |
| KVH Casting Limited | Administrative & support | 2016 |
| KVZ London Ltd | Professional & scientific | 2014 |
| Kwik Lettings Limited | Real estate | 2020 |
| Kwil Legal Services Ltd | Professional & scientific | 2021 |
| Kwperformance&Lifestyle Limited | Other services | 2023 |
| Kyle Mann Ltd | Information & communication | 2016 |
| Kylha Group Ltd | Administrative & support | 2023 |
| Kylha Properties Limited | Real estate | 2025 |
| Kynetic Ltd | Real estate | 2025 |
| Kynsi Limited | Wholesale & retail | 2022 |
| Kyte Associates Ltd | Professional & scientific | 2010 |
| KZH Consultancy Limited | Professional & scientific | 2016 |
| L & B Builders Ltd | Construction | 2014 |
| L & J Kingsley Property Ltd | Real estate | 2019 |
| L & M Electrical Limited | Construction | 2015 |
| L & M Upholstery Ltd | Other services | 2016 |
| L a F Education Limited | Education | 2024 |
| L a H Education Limited | Education | 2024 |
| L a N Education Limited | Education | 2024 |
| L Evgenidis Datalogic Solutions Ltd | Information & communication | 2021 |
| L JAY Engineering Ltd | Professional & scientific | 2026 |
| L JAY Properties Ltd | Real estate | 2026 |
| L K Online Ltd | Wholesale & retail | 2025 |
| L O Enterprise Ltd | Information & communication | 2018 |
| L P W Computer Services Limited | Information & communication | 1996 |
| L Smith Site Services Limited | Construction | 2021 |
| L Systems Ltd | Information & communication | 2019 |
| L&A Automotive Ltd | Wholesale & retail | 2015 |
| L&M Holding Ltd | Professional & scientific | 2014 |
| L&M Roche Homes Limited | Real estate | 2025 |
| L'Arte Sea Food & Grill Limited | Hospitality | 2023 |
| L'Azur Ltd | Wholesale & retail | 2017 |
| L.E.C. Solutions Limited | Information & communication | 2014 |
| L.R. Heating & Electrical Services Ltd | Construction | 2004 |
| L13 Limited | Professional & scientific | 2021 |
| L2P Watford Driving School Ltd | Education | 2023 |
| L5 Limited | Financial services | 2020 |
| LA Bocadillo Ltd | Hospitality | 2023 |
| LA Capital Group Ltd | Financial services | 2023 |
| LA Denisa Dolce Limited | Hospitality | 2025 |
| LA Dental Limited | Other services | 2016 |
| LA Entertainments Ltd | Arts & recreation | 2024 |
| LA Maison DE Luxe Contracts Ltd | Construction | 2025 |
| LA Mart Watford Limited | Wholesale & retail | 2025 |
| LA Petite Brassiere Ltd | Hospitality | 2018 |
| LA Pointe Consulting Ltd | Administrative & support | 2023 |
| LAB Refrigeration Limited | Manufacturing | 2010 |
| LAB Services Limited | Professional & scientific | 1996 |
| Label Supplies UK Ltd | Wholesale & retail | 2013 |
| Labiuc Ltd | Transport & logistics | 2020 |
| Labmode Limited | Professional & scientific | 2007 |
| Lace Hill Commercial Finance Ltd | Financial services | 2024 |
| Laci Rose Ltd | Construction | 2022 |
| Ladak Enterprises Limited | Professional & scientific | 2012 |
| Ladi & Nadia Investment Limited | Real estate | 2026 |
| Ladnek Limited | Real estate | 2013 |
| Lady Routier Limited | Transport & logistics | 2022 |
| Ladyyo Limited | Households | 2025 |
| LAEM78 Ltd | Education | 2025 |
| Lafford & Moore Limited | Manufacturing | 1977 |