| In-Pact Accountancy Ltd | Administrative & support | 2007 |
| IN2YOGA Limited | Professional & scientific | 2003 |
| Inch Communications Limited | Information & communication | 2005 |
| Incompass Associates Limited | Professional & scientific | 2006 |
| Incubation Limited | Arts & recreation | 2003 |
| Independent Catering Ltd | Extraterritorial | 2002 |
| Independent Catering Management Limited | Hospitality | 1996 |
| Independent Forklift Engineers Limited | Manufacturing | 2005 |
| Independent Industrial Supplies (Guildford) Limited | | 1979 |
| Independent Lifestyle Options DCA Ltd | Health & social care | 2009 |
| Indespray Limited | Wholesale & retail | 2003 |
| Index Business Solutions Limited | Information & communication | 2004 |
| Indiana Tandoori Limited | Hospitality | 2020 |
| Indigo Jade Limited | Information & communication | 1992 |
| Indus Lifespace Ltd | Wholesale & retail | 2019 |
| Industrial Chemicals & Equipment Limited | Wholesale & retail | 1987 |
| Industrial Climates Control Limited | | 1969 |
| Inet Infotech Limited | Information & communication | 1997 |
| Information Developments Limited | Information & communication | 1983 |
| Information Management Services Limited | Professional & scientific | 2008 |
| Information Technology Management Limited | Information & communication | 1996 |
| Infostress PVT. Ltd | Construction | 2013 |
| Inglewood Palm Hotel Limited | Hospitality | 2013 |
| Initiative Sports Marketing Limited | Other services | 1994 |
| Inline Computer Services (UK) Limited | Information & communication | 1992 |
| Inline Solutions Limited | Other services | 2004 |
| Inner EYE Limited | Information & communication | 1993 |
| Inner Strength Network CIC | Education | 2015 |
| Innovative Data Services Ltd | Construction | 2024 |
| INR Initiative Ltd | Information & communication | 2017 |
| Insanely Good Limited | Professional & scientific | 2025 |
| Insight Corporation Limited | Information & communication | 2002 |
| Insight Plays Ltd | Information & communication | 2025 |
| Inspiery Ltd | Information & communication | 2023 |
| Inspira Limited | Information & communication | 1995 |
| Inspiration Developments Limited | Real estate | 2007 |
| Inspired Marketing Strategies Limited | Professional & scientific | 2008 |
| Inspired Short Stays Ltd | Real estate | 2020 |
| Inspiring Software Limited | Information & communication | 2001 |
| Instant Team Support Ltd | Health & social care | 2017 |
| Instructasolicitor Limited | Professional & scientific | 2001 |
| Insurance Warehouse Premium Finance Ltd | Financial services | 2006 |
| Insureeasy Ltd | Financial services | 2003 |
| Intacom Security Systems Limited | Professional & scientific | 1988 |
| Integra Training Limited | Professional & scientific | 2003 |
| Integrity Construction Ltd | Construction | 2005 |
| Intelligent Growth Limited | Professional & scientific | 2002 |
| Intelligent Power Limited | Administrative & support | 2006 |
| Inter-Continental Petroleum Company Limited | Mining & quarrying | 2001 |
| Interactive Educational Systems International Limited | Administrative & support | 1988 |
| Interactive Video Epoch Productions Limited | Administrative & support | 1989 |
| Intercreed Limited | Information & communication | 2014 |
| Interfitfix Interiors Limited | Construction | 2018 |
| Interiors of Distinction Limited | Other services | 1994 |
| International Marketing Networks Limited | Wholesale & retail | 2008 |
| International Peace Research Association | Professional & scientific | 2026 |
| Interscope Productions Limited | Professional & scientific | 2006 |
| Intertec Data Solutions Limited | Information & communication | 2003 |
| Intertech Software Limited | Information & communication | 2004 |
| Inthira Food Service Limited | Hospitality | 2024 |
| Introversion Software Limited | Information & communication | 2002 |
| Inventas Limited | Information & communication | 1998 |
| Investments 88 Limited | Financial services | 2024 |
| Investors Property Corporation Limited(The) | Real estate | 1894 |
| Invista Limited | Manufacturing | 1994 |
| Inyatsi UK Limited | Construction | 2023 |
| IP6NET Ltd | Information & communication | 2003 |
| IPR Industries Limited | Administrative & support | 1992 |
| IPR Property Limited | Real estate | 2007 |
| Iqtelligent Limited | Professional & scientific | 2002 |
| Irchcom Rail Ltd | Transport & logistics | 2017 |
| Irpm Limited | Professional & scientific | 2004 |
| ISA A.V. Ltd | Professional & scientific | 2005 |
| Isca Management Limited | Professional & scientific | 2002 |
| Island Systems Ltd | Information & communication | 1998 |
| Isomob Limited | Information & communication | 2005 |
| Issco Limited | Wholesale & retail | 2002 |
| IT IS IT Limited | Information & communication | 2002 |
| It's A...Wrap FG Ltd | Hospitality | 2015 |
| IT4AUTOMATION Limited | Information & communication | 2006 |
| IT4U Limited | Information & communication | 2005 |
| Italia Conti Weekend Associates Limited | Administrative & support | 2006 |
| Italian Delights Limited | Administrative & support | 2009 |
| Ithaki Limited | Professional & scientific | 2003 |
| ITR Limited | Professional & scientific | 2008 |
| IVY Ekong Limited | Wholesale & retail | 2011 |
| IVY Services Ltd | Other services | 2005 |
| Iwebma Limited | Information & communication | 2007 |
| Iykons Accounting Services Ltd | Professional & scientific | 2012 |
| Iykons Business Services Ltd | Professional & scientific | 2012 |
| Iykons Innovation and Consultancy Limited | Information & communication | 2014 |
| Iykons IT Services Ltd | Information & communication | 2012 |
| Iykons Limited | Information & communication | 2008 |
| Izolart Systems Ltd | Construction | 2014 |
| J & B Carroll Limited | Professional & scientific | 2002 |
| J & C Property Ltd | Real estate | 2005 |
| J & LK Property Limited | Real estate | 2021 |
| J & S Consultants | | 1985 |
| J & T Limited | Hospitality | 1999 |
| J a G Gardening Limited | Other services | 2005 |