| Independent Dental Plans Limited | Health & social care | 2004 |
| Independent Reports Limited | Professional & scientific | 2023 |
| Independent Systems Marketing Ltd | Wholesale & retail | 2018 |
| Inderflame Combustion and Heating Services Limited | Professional & scientific | 1978 |
| Indigo Indemnity Limited | Financial services | 2017 |
| Inductotherm Europe Limited | Manufacturing | 1936 |
| Industria Group Ltd | Construction | 2019 |
| Industrial Property Advice Limited | Professional & scientific | 2023 |
| Informed Executives (Europe) Limited | Administrative & support | 2011 |
| Informed People Limited | Administrative & support | 2013 |
| Informed Professionals Ltd | Professional & scientific | 2012 |
| Ingenium Engineering Solution Ltd | Professional & scientific | 2015 |
| INK Stitch & Decals Ltd | Wholesale & retail | 2026 |
| Innosteel Consult Limited | Professional & scientific | 2021 |
| Innovation VAT Services Limited | Professional & scientific | 2015 |
| Innovativec Limited | Manufacturing | 2025 |
| INO Technologies Ltd | Professional & scientific | 2020 |
| Inoxi Holdings Limited | Financial services | 2023 |
| Insight Solutions IT Services Limited | Information & communication | 2002 |
| Integro PM Limited | Construction | 2022 |
| Inter Research Partners Limited | Information & communication | 2021 |
| Interactive Healthcare Training Ltd | Education | 2011 |
| Interactive Minds International Limited | Wholesale & retail | 2008 |
| Interdev Consultants Ltd | Information & communication | 2018 |
| Interim Accountants Limited | Professional & scientific | 2009 |
| International Monetary Investments Limited | Financial services | 2021 |
| Invatax Ltd | Information & communication | 2026 |
| Invico Limited | Real estate | 2018 |
| Iona Davis Ltd | Professional & scientific | 2016 |
| Iona Tech Ltd | Information & communication | 2014 |
| Ircm Limited | Professional & scientific | 2015 |
| Ircm Properties Ltd | Real estate | 2016 |
| IT Epos Group Limited | Information & communication | 2023 |
| IT Solutions QED Ltd | Information & communication | 2011 |
| IT Tactical Limited | Information & communication | 2015 |
| Itaa Holdings Ltd | Financial services | 2021 |
| Itaa Ltd | Information & communication | 2019 |
| Itaa.Ai Limited | Information & communication | 2026 |
| Itaara Limited | Information & communication | 2026 |
| Itixa Ltd | Information & communication | 2024 |
| Iustus Limited | Administrative & support | 2007 |
| J & a Leisure Limited | Other services | 2011 |
| J & D Care Services Limited | Financial services | 2024 |
| J & H Estates Limited | Administrative & support | 2005 |
| J a Property Group Limited | Real estate | 2017 |
| J and T Haulage Limited | Transport & logistics | 2013 |
| J Field Construction Ltd | Construction | 2024 |
| J L Rendering Limited | Construction | 2019 |
| J Moore Electrical Ltd | Construction | 2024 |
| J R Management Accountancy Limited | Professional & scientific | 2016 |
| J Shrubb Ltd | Arts & recreation | 2026 |
| J T Rights Limited | Administrative & support | 2009 |
| J Terry Services Ltd | Construction | 2020 |
| J W Smart Meters Ltd | Administrative & support | 2013 |
| J Wasserberg Limited | Administrative & support | 2011 |
| J.G. Molloy Building Contractors Limited | Construction | 2023 |
| J.G. Molloy Limited | Construction | 2001 |
| J.M. Bourne Limited | Manufacturing | 2009 |
| J2COM Limited | Information & communication | 2004 |
| Jacaustom Limited | Real estate | 2013 |
| Jack Cotterill Tree Services Limited | Agriculture & fishing | 2014 |
| Jakel Limited | Administrative & support | 2021 |
| JAM Ideas Holdings Limited | Financial services | 2022 |
| Jambo Ventures Ltd | Wholesale & retail | 2019 |
| James Evans Surveyors Ltd | Professional & scientific | 2026 |
| James Kirby Associates Ltd | Administrative & support | 2022 |
| James Lewis Capital Limited | Real estate | 2021 |
| James Triner Limited | Arts & recreation | 2025 |
| James Ward Creative Limited | Information & communication | 2024 |
| Jamie Richard Ward Ltd | Information & communication | 2026 |
| Jane Newman Financial Planning Limited | Administrative & support | 2011 |
| Jarrowood Holdings Limited | Financial services | 2026 |
| Jarrowood Limited | Financial services | 2004 |
| Jasmin PT Ltd | Other services | 2019 |
| Jawhari Endoscopy Limited | Health & social care | 2023 |
| Jaydubya Productions Limited | Administrative & support | 2010 |
| JB Driving & Plant Services Limited | Transport & logistics | 2015 |
| Jbat Theatre Limited | Arts & recreation | 2022 |
| JBS Property Services Limited | Real estate | 2018 |
| Jbsm Recruitment Ltd | Administrative & support | 2025 |
| JC Plant Machinery Limited | Administrative & support | 2025 |
| JC Utility ARB Limited | Agriculture & fishing | 2025 |
| JCP Medical Ltd | Health & social care | 2019 |
| JD Building Ltd | Construction | 2019 |
| JD Financial Translations Limited | Administrative & support | 2013 |
| JDN Siviter Holdings Limited | Financial services | 2013 |
| JE Automation Ltd | Wholesale & retail | 2025 |
| Jeff Zindani & Associates Limited | Professional & scientific | 2014 |
| Jehad KRD Ltd | Wholesale & retail | 2025 |
| Jenad Medical Limited | Health & social care | 2022 |
| Jenrea Trading Ltd | Wholesale & retail | 2026 |
| Jeremy Billingham Aerials Ltd | Information & communication | 2021 |
| Jergixiouz Ltd | Hospitality | 2024 |
| Jessflo LLP | | 2011 |
| JET RES Ltd | Manufacturing | 2025 |
| JET Resources Ltd | Manufacturing | 2011 |
| Jewffee UK Limited | Wholesale & retail | 2021 |
| Jezi Ltd | Real estate | 2026 |
| JFA Accountancy Limited | Professional & scientific | 2003 |
| Jibsheen Productions Limited | Arts & recreation | 2017 |