| Itvantage Systems Limited | Information & communication | 2001 |
| Ivex 1974 Ltd | Transport & logistics | 2016 |
| IVY Carpentry Ltd | Manufacturing | 2021 |
| IVY Villas Freehold Limited | Households | 2015 |
| J R Aesthetics Limited | Other services | 2018 |
| J V Electrical & Security Limited | Other services | 2017 |
| J V Scaffolding Limited | Construction | 2018 |
| J.D. Estates Ltd | Real estate | 2003 |
| J2J Ltd | Construction | 2025 |
| JA Accountancy Ltd | Professional & scientific | 2022 |
| JAI Medina Limited | Construction | 2025 |
| Jaimie's Limited | Wholesale & retail | 2014 |
| JAN & Lily Limited | Transport & logistics | 2013 |
| Janice Chissick Estates Limited | Real estate | 2006 |
| Jarvis Creative Limited | Professional & scientific | 2023 |
| JAS Candles Ltd | Manufacturing | 2025 |
| Jasak Properties Ltd | Real estate | 2019 |
| Jashn - E - Utsav Events and Occasions Ltd | Administrative & support | 2021 |
| JB Fit-Out Ltd | Construction | 2017 |
| JBG Property Investments Ltd | Real estate | 2019 |
| JD London Ltd | Construction | 2018 |
| Jdjps Group Limited | Professional & scientific | 2010 |
| Jdktrades Ltd | Wholesale & retail | 2025 |
| JDT Heating & Plumbing Ltd | Construction | 2019 |
| JEH Solutions Ltd | Construction | 2026 |
| Jeny Property Ltd | Real estate | 2017 |
| Jesus Lives-Uk Evangelical International Ministry Ltd | Other services | 2019 |
| JG Goods Ltd | Wholesale & retail | 2023 |
| Jglow Skincare Ltd | Other services | 2025 |
| JI Strategic Ltd | Financial services | 2026 |
| Jimtas Healthcare Limited | Health & social care | 2023 |
| Jivco Ltd | Construction | 2016 |
| JJ Medical Ltd | Health & social care | 2025 |
| Jkbt Limited | Arts & recreation | 2021 |
| JL Swim School Ltd | Education | 2025 |
| Jlux Estates Ltd | Real estate | 2025 |
| Jmuk Solutions Ltd | Administrative & support | 2025 |
| JNR Mayor Limited | Real estate | 2024 |
| Jochebed Homes Limited | Health & social care | 2020 |
| Joel Property Developments Limited | Construction | 2015 |
| John Logistics & Courier Ltd | Transport & logistics | 2022 |
| John’S Naturals Ltd | Wholesale & retail | 2025 |
| Joint AK Property Ltd | Real estate | 2021 |
| Joint Enterprise London Limited | Health & social care | 2015 |
| Jolly Futures CIC | Information & communication | 2019 |
| Joni Ltd | Construction | 2025 |
| Jordan Harper Estates Ltd | Real estate | 2025 |
| Joserinu Ltd | Information & communication | 2011 |
| Josh's Local Service's Ltd | Administrative & support | 2026 |
| JPS Consultants Limited | Information & communication | 2001 |
| JS Medi Ltd | Real estate | 2021 |
| JS Prop Group Ltd | Real estate | 2024 |
| JS R2R Ltd | Real estate | 2025 |
| JSA Ventures Ltd | Wholesale & retail | 2025 |
| JSK Entertainment Limited | Wholesale & retail | 2011 |
| JSK MV Properties Ltd | Real estate | 2024 |
| JSM Retail Sentinel Ltd | Construction | 2024 |
| Juliana Properties Limited | Real estate | 2019 |
| Julius & Svetla Ltd | Construction | 2019 |
| Juno Properties Ltd | Real estate | 2022 |
| Just Spirits Ltd | Other services | 2016 |
| K & J Management Ltd | Extraterritorial | 2016 |
| K & K Flooring & Construction Ltd | Construction | 1996 |
| K Mesiu Energy Ltd | Other services | 2021 |
| K&A UK Properties Ltd | Real estate | 2022 |
| K&K Precision Solutions Ltd | Construction | 2025 |
| K&R Cleaners Limited | Administrative & support | 2025 |
| K&R R Ltd | Real estate | 2020 |
| K-L1NA Limited | Professional & scientific | 2026 |
| KA Commercials Ltd | Wholesale & retail | 2025 |
| KA Windows and Doors Ltd | Construction | 2011 |
| Kabris Estates Ltd | Real estate | 2026 |
| Kahh Properties Ltd | Real estate | 2023 |
| Kahlon Consultancy Ltd | Real estate | 2014 |
| Kailas Property Ventures Ltd | Real estate | 2022 |
| Kailas Vision Ltd | Hospitality | 2024 |
| Kajj Medical Services Limited | Professional & scientific | 2007 |
| Kalvibykv Ltd | Education | 2026 |
| Kapil Kuteer Consultancy Limited | Health & social care | 2022 |
| Kareem Management Limited | Real estate | 2023 |
| Karlon Enterprises Ltd | Financial services | 2025 |
| Kartar & Sons LLP | | 2013 |
| Kassiadies Services Ltd | Professional & scientific | 2015 |
| Katesowerby Ltd | Professional & scientific | 2022 |
| Kaur & Co Properties Ltd | Real estate | 2022 |
| Kaur Kidsdent Ltd | Health & social care | 2023 |
| Kavin Ltd | Health & social care | 2012 |
| Kawawa Kollection Ltd | Wholesale & retail | 2025 |
| Kayes Accountancy Limited | Professional & scientific | 2019 |
| Kayoski Care Ltd | Health & social care | 2020 |
| KB Carpentry Ltd | Manufacturing | 2021 |
| KC11 Security Ltd | Real estate | 2023 |
| KDJ Development Ltd | Construction | 2025 |
| Kearin Properties Limited | Real estate | 2016 |
| Kech Consulting Ltd | Information & communication | 2018 |
| Kelbsco Ltd | Administrative & support | 2018 |
| KEM. Brickwork Ltd | Construction | 2025 |
| Kemikal Media Europe Ltd | Information & communication | 2023 |
| Kemikal Works Limited | Information & communication | 2021 |
| Kent Camera Ltd | Information & communication | 2019 |