| Ineos E&P (UK) II Limited | Lyndhurst | 2024 |
| Ineos E&P (UK) Limited | Lyndhurst | 2002 |
| Ineos Energy E&P Holdings II Limited | Lyndhurst | 2024 |
| Ineos Energy E&P Holdings III Limited | Lyndhurst | 2024 |
| Ineos Energy E&P Holdings Limited | Lyndhurst | 2024 |
| Ineos FPS Limited | Lyndhurst | 2017 |
| Ineos Offshore BCS Limited | Lyndhurst | 2015 |
| Ineos UK E&P Holdings Limited | Aberdeen | 1999 |
| Ineos UK SNS Limited | Lyndhurst | 1971 |
| Ineos Upstream Holdings Limited | Lyndhurst | 2017 |
| Ineos Upstream Limited | Lyndhurst | 2014 |
| Ineos Upstream Services Limited | Lyndhurst | 2015 |
| Infinity Exploration Limited | Bridgend | 2017 |
| Infinity Marine Services Ltd | Witham | 2020 |
| Infinity Stone Limited | Uckfield | 2012 |
| Infiverde Limited | Leatherhead | 2016 |
| Infrastrata UK Limited | London | 2006 |
| Infrastructure Analytics Limited | Belfast | 2016 |
| Ingrebourne PFA Ltd | Harlow | 2016 |
| Ingrebourne Valley Limited | Harlow Common Harlow | 1993 |
| Inishowen Associates Limited | Banchory | 2017 |
| Initiam Commodity Partners Ltd | London | 2025 |
| Inland Engineering Services Ltd. | Motherwell | 2005 |
| Inland Metal & Mining Company Ltd | London | 2014 |
| Inmec Limited | Croydon | 1985 |
| Innes Access & Construction Limited | Tain | 2009 |
| Innova Drilling and Intervention Limited | Aberdeen | 2011 |
| Innovative Engineering Systems Limited | Edinburgh | 1994 |
| Innowingspan UK Commerce and Solutions Ltd | West Midlands, England | 2025 |
| Innox Petroleum Trading Company Ltd | Grays | 2025 |
| Inpex Angola Block 14 Ltd. | London | 2012 |
| Inpex Malaysia E&P 2A Limited | London | 2023 |
| Inpipe Technical Limited | Jarrow | 2007 |
| Inside OUT Building Services Limited | Hillingdon | 2017 |
| Insight Global Ventures Synergy Ltd | Edinburgh | 2024 |
| Inspec-Ts Global Ltd | Cardiff | 2020 |
| Integra Well Solutions Limited | Aberdeen | 2018 |
| Integral Energy (Inc) Limited | Milton Keynes | 2021 |
| Integrale Engineering Limited | Edinburgh | 2013 |
| Integrated Reservoir Solutions Limited | Chester | 1998 |
| Integrated Safety Solutions Limited | Redcar | 2014 |
| Integrated Services (Intl) Limited | Aberdeen | 1997 |
| Integrated Upstream Solutions Limited | Reading | 2017 |
| Integrated Valve Solutions Ltd | Ellon | 2011 |
| Integrated Waterflood Management Limited | Liverpool | 2018 |
| Integrative Geoscience Limited | Woking | 2012 |
| Integrity Engineering O&G Ltd | Thame | 2011 |
| Integrity Support Solutions Group Limited | Moffat | 2004 |
| Inteliwell Limited | Birmingham | 2023 |
| Intelligent Geographic Target Identification (Igti) Ltd | Huntingdon | 2025 |
| Intelligo Solutions Limited | Hook Heath | 2016 |
| Inter-Continental Petroleum Company Limited | Surrey | 2001 |
| Inter-Power UK Limited | Lutterworth | 1987 |
| Interactive Petrophysics Ltd. | Aberdeen | 1998 |
| Interafcon Limited | Bolton | 2017 |
| Interconnect Engineering Limited | Whitby | 2024 |
| Interface Engineering Services Limited | Great Yarmouth | 2001 |
| Intermara Marine Limited | Aberdeen | 2023 |
| Intermetal Limited | London | 2005 |
| Internal Surveys Limited | Portsmouth | 2007 |
| International Auditing and Accounting Services Limited | Glasgow | 1999 |
| International B2G Consortium Ltd | Newcastle Upon Tyne | 2010 |
| International Battery Metals Ltd | London | 2018 |
| International Creative Technologies Ltd | Walton-On-Thames | 2012 |
| International Group Investments Ltd | London | 2025 |
| International Inspection Services Limited | Washington | 2018 |
| International Jade Jewelry Industry Association | Beckenham | 2023 |
| International Lifting Services Ltd | Kirkcaldy | 2026 |
| International Logging Technology Limited | London | 1990 |
| International Metal and Mineral Agents Limited | Crook | 1975 |
| International Mineral Resources Agromineral Sudan Ltd | Bexleyheath | 2026 |
| International Mineral Resources Ltd | St. Ives | 2018 |
| International Mining & Infrastructure Corporation PLC | Birmingham | 2004 |
| International Oilfield Services Ltd | Prestwick | 2016 |
| International Petrogas Company Ltd | Stoke-On-Trent | 2025 |
| International Pipeline Structural Solutions Limited | Wolverhampton | 2014 |
| International Quarrying Consultants Limited | Stroud | 1967 |
| International Security Deposits Ltd. | Leeds | 2015 |
| International Stone Ltd | Liskeard | 2001 |
| International TIN Association Ltd | St Albans | 1994 |
| International Trading (IT) Limited | London | 1996 |
| International Tubular Services Limited | Aberdeen | 1988 |
| Interocean Marine Services Limited | Aberdeen | 2007 |
| Intervention Rentals International Limited | By Montrose | 2017 |
| Intervention Solutions Limited | Great Yarmouth | 2026 |
| Interwell Limited | Aberdeen | 2011 |
| Inuit Europe Ltd | West Midlands, England | 2025 |
| Inventable Technologies Limited | Petersfield | 2015 |
| Invepetrol Limited | London | 2011 |
| Inverleith Holdings Limited | Edinburgh | 2020 |
| Investco Portfolio Limited | Bromley | 2017 |
| Investment & Development Mining Resources Ltd | London | 2016 |
| Invictus Investments Holding Ltd | Cardiff | 2021 |
| Invigilo Limited | St. Ives | 2016 |
| Invinceus Group Ltd | Dundee | 2013 |
| Invinceus International Ltd | Dundee | 2013 |
| Invinceus Ltd | Dundee | 2013 |
| Ioan Morris (Electrical) Ltd | London | 2017 |
| IOG Energies Limited | London | 2022 |
| IOG PLC | London | 2010 |