| In-Region Ltd | Information & communication | 2020 |
| Inclusive Improvement Ltd | Education | 2025 |
| Index East Anglia Limited | Other services | 2015 |
| Index Property Information Lincolnshire Limited | Other services | 2014 |
| Indigo 2021 Ltd | Wholesale & retail | 2021 |
| Indigo Group Topco Ltd | Information & communication | 2022 |
| Indigo Software (Holdings) Limited | Professional & scientific | 2012 |
| Indigo Software Group Limited | Information & communication | 2016 |
| Indigo Software Limited | Information & communication | 2005 |
| Indiyna Home Ltd | Other services | 2025 |
| Infinite Renewable Energy Limited | Construction | 2019 |
| Infrared Heating Products Limited | Manufacturing | 2016 |
| Infrastructure Planning and Design Limited | Professional & scientific | 2010 |
| Infused Food Limited | Hospitality | 2018 |
| Ingatestone Grove Management Company Limited | Households | 2025 |
| Inglenook Development Limited | Real estate | 2022 |
| Initial IT Solutions Limited | Information & communication | 2006 |
| Inner Circle Developments Limited | Real estate | 2012 |
| Innkka Developments Limited | Real estate | 2019 |
| Innkka Ltd | Real estate | 2017 |
| Innovative Testing Solutions Limited | Administrative & support | 2018 |
| Inposterum Ltd | Information & communication | 2025 |
| Inside OUT Environmental Limited | Water & waste | 2007 |
| Inside OUT Management Limited | Professional & scientific | 2007 |
| INSIGHT54 Limited | Professional & scientific | 2025 |
| Inspire Actors Studio Limited | Arts & recreation | 2016 |
| Inspire and Connect Ltd | Administrative & support | 2021 |
| Inspire Cloud Limited | Information & communication | 2018 |
| INSPIRE2TRAIN With Helen Ltd | Health & social care | 2008 |
| Inspired Accountants Holdings Limited | Financial services | 2024 |
| Inspired Accountants Limited | Professional & scientific | 2004 |
| Inspired Clarity Limited | Professional & scientific | 2019 |
| Instalek Limited | Professional & scientific | 2014 |
| Instalmnts Ltd | Financial services | 2025 |
| Integral Communications Limited | Extraterritorial | 1997 |
| Integral Communications Network Services Limited | Extraterritorial | 2010 |
| Integralcomm.Co.Uk Limited | Information & communication | 2001 |
| Integrated System Technologies Limited | Information & communication | 1997 |
| Intellegere Ltd | Administrative & support | 2015 |
| Interactive Scheduling Products Ltd | Information & communication | 2012 |
| Interactivesp Ltd | Information & communication | 2009 |
| Interlace Property Ltd | Real estate | 2019 |
| Interlock Group Limited | Financial services | 2026 |
| International Dragon Limited | Wholesale & retail | 2017 |
| International Tank Container Organisation Limited | Other services | 2025 |
| Interpritalia Language Services Ltd | Professional & scientific | 2012 |
| Interstitial Lung Disease - Interdisciplinary Network Limited | Other services | 2016 |
| Inukshuk Developments Limited | Construction | 2017 |
| Invigopro Limited | Wholesale & retail | 2025 |
| Inyama Restaurant Ltd | Hospitality | 2023 |
| IOF International Academy Limited | Arts & recreation | 2023 |
| ION Installations Ltd | Construction | 2023 |
| Iona Servics Limited | Health & social care | 2025 |
| Ionerefest Ltd | Administrative & support | 2021 |
| IPA Leisure Limited | Real estate | 2005 |
| IPA Tennis Limited | Real estate | 1972 |
| Ipcompute UK Ltd | Information & communication | 2019 |
| Iplaceuk Limited | Administrative & support | 2019 |
| IPS Worldwide Limited | Administrative & support | 2014 |
| Irobotics Ltd | Information & communication | 2007 |
| Iron INK Group Ltd | Information & communication | 2026 |
| Iserphons Ltd | Administrative & support | 2021 |
| ISO Academy Limited | Education | 2020 |
| ISO Quality Support Limited | Professional & scientific | 2019 |
| Ispayce Limited | Information & communication | 2021 |
| IT Total Solutions Limited | Information & communication | 2005 |
| Italia(Uk) Ltd | Wholesale & retail | 2026 |
| Ivory Ventures Limited | Professional & scientific | 2025 |
| Ivysar Ltd | Real estate | 2019 |
| Iwma Ltd | Other services | 2016 |
| J & C Eagles Ltd | Construction | 2017 |
| J & G Building Contractors Ltd | Construction | 2019 |
| J Barlow Training Limited | Information & communication | 2024 |
| J Breadon Home and Electrical Ltd | Construction | 2024 |
| J Campbell Associates Limited | Real estate | 2025 |
| J Door & Window Ltd | Construction | 2023 |
| J H Components Limited | Wholesale & retail | 1996 |
| J J Megan (Farriers) Ltd | Agriculture & fishing | 2003 |
| J M Tattoos Limited | Other services | 2016 |
| J P Insolvency Services Limited | Water & waste | 1976 |
| J R Hindley Limited | Manufacturing | 2003 |
| J R Properties (Staffs) Limited | Real estate | 2011 |
| J S Shelley Ltd | Financial services | 2026 |
| J Shelley Limited | Real estate | 2009 |
| J T Design Partnership LLP | | 2008 |
| J&K Logistics Ltd | Transport & logistics | 2018 |
| J'S Auto Electrical Solutions Ltd | Wholesale & retail | 2022 |
| J-Log Solutions Ltd | Professional & scientific | 2010 |
| J. Howell & Daughters Limited | Other services | 2012 |
| J.Grant Electrical Solutions Ltd | Construction | 2024 |
| J.L.S. Sport Ltd. | Wholesale & retail | 1997 |
| J2 Electrical Solutions Ltd | Construction | 2024 |
| Jaama Ltd | Information & communication | 2004 |
| JAB Buildings Ltd | Administrative & support | 2023 |
| JAB Logistics Midlands Limited | Transport & logistics | 2018 |
| JAC & JON Limited | Wholesale & retail | 2018 |
| Jack & Jill's Pre-School (Lichfield) | Education | 2008 |
| Jack Frost Hire Ltd | Manufacturing | 2018 |
| Jackshoot.Com Limited | Information & communication | 2006 |
| Jackson Electrical Services & Contractors Holdings Ltd | Administrative & support | 2016 |