| Info Radiance Ltd | Information & communication | 2012 |
| Infogoo Ltd | Information & communication | 2005 |
| Infonium Limited | Information & communication | 2018 |
| Informational Limited | Real estate | 2025 |
| Informatiq Consulting Limited | Information & communication | 1994 |
| Infoscale Ltd | Professional & scientific | 2011 |
| Infotech Solutions Services Ltd | Information & communication | 2015 |
| INFOTECH21 Ltd | Information & communication | 2013 |
| Infovesta Limited | Information & communication | 2011 |
| Infozone Limited | Administrative & support | 2017 |
| Infra Dynamic Ltd | Information & communication | 2019 |
| Infratest Services UK Ltd | Other services | 2026 |
| Infront Financial Information Limited | Professional & scientific | 2015 |
| Ingefi Conseil Ltd | Professional & scientific | 2017 |
| Ingex UK Ltd | Manufacturing | 2020 |
| Inginerul Limited | Manufacturing | 2015 |
| Ingle-Woodgrove Ltd | Administrative & support | 2018 |
| Ingles Trading Limited | Wholesale & retail | 2024 |
| Ingracio Limited | Real estate | 2026 |
| Ingram and SON Ltd | Construction | 2014 |
| Ingram Finance Limited | Administrative & support | 2009 |
| Inhurst Trade Services Ltd | Construction | 2025 |
| Initivo Consultancy Limited | Construction | 2005 |
| Iniya Tamil Ltd | Real estate | 2024 |
| Injectors Initiative Ltd | Education | 2026 |
| INK (Clothing) Limited | Wholesale & retail | 1993 |
| INK Threads Limited | Wholesale & retail | 2023 |
| Inkorp Limited | Administrative & support | 2024 |
| Inktech Solutions Limited | Information & communication | 2015 |
| Inlo Ltd | Professional & scientific | 2025 |
| Inniss Miller & Stadden Ltd | Information & communication | 2014 |
| Innospect Ltd | Professional & scientific | 2025 |
| Innotif Limited | Information & communication | 2014 |
| INNOV8 Construct Ltd | Construction | 2023 |
| Innovais Elabs Ltd | Information & communication | 2025 |
| Innovate Today Limited | Professional & scientific | 2023 |
| Innovation Education Ltd | Education | 2023 |
| Innovation Mews Ltd | Real estate | 2020 |
| Innovative Financial Consulting Limited | Professional & scientific | 2015 |
| Innovative Heat Pump Solutions Limited | Professional & scientific | 2024 |
| Innovative-Change Ltd | Professional & scientific | 2013 |
| Innovis Consult Ltd | Construction | 2024 |
| Inothink Ltd | Health & social care | 2022 |
| Inovative Finds Ltd | Wholesale & retail | 2026 |
| Inpha LLP | | 2012 |
| Inpodi Ltd | Manufacturing | 2025 |
| Inpro International UK Limited | Wholesale & retail | 2019 |
| Input Media Limited | Extraterritorial | 2005 |
| Input Video Holdings Ltd | Information & communication | 2015 |
| Input Video Ltd | Information & communication | 1987 |
| Inquisitive Insight Ltd | Professional & scientific | 2017 |
| Inrush Ltd | Professional & scientific | 2011 |
| Inrush Properties Ltd | Real estate | 2017 |
| Inside OUT Fashion Studio Ltd | Wholesale & retail | 2022 |
| Insideout Corporation Limited | Information & communication | 2019 |
| Insight Command Limited | Wholesale & retail | 2025 |
| Insight ORE Ltd | Information & communication | 2016 |
| Insight Private Limited | Information & communication | 2014 |
| Insightful Marketing Ltd | Wholesale & retail | 2025 |
| Insinkerator UK Ltd | Wholesale & retail | 1959 |
| Inspire Bar Group Ltd | Wholesale & retail | 2019 |
| Inspire Beverages Ltd | Professional & scientific | 2016 |
| Inspire Builders Limited | Construction | 2011 |
| Inspire Developments (Group) Ltd | Real estate | 2020 |
| Inspire Edpsych Ltd | Education | 2023 |
| Inspire Group Ltd | Construction | 2015 |
| Inspire Housing Ltd | Real estate | 2014 |
| Inspire Music School Limited | Education | 2016 |
| Inspired Equity Commercial Ltd | Real estate | 2022 |
| Inspired Equity Holdings Ltd | Real estate | 2025 |
| Inspired Equity Partners Limited | Real estate | 2016 |
| Inspired OUD Limited | Wholesale & retail | 2026 |
| Inspireher Global Community Interest Company | Education | 2025 |
| Inspireinvest Estate Ltd | Real estate | 2025 |
| Inspiring Progress CIC | Health & social care | 2011 |
| Instant Housing Limited | Real estate | 2018 |
| Institute of Grocery Distribution (the) | Professional & scientific | 1909 |
| Instrotech Holdings Limited | Wholesale & retail | 1984 |
| Instrotech Limited | Wholesale & retail | 2021 |
| Insuha Limited | Real estate | 2020 |
| Int'L Centre for Family Law, Policy and Practice Limited | Other services | 2014 |
| Intechlect Consultancy Services Limited | Information & communication | 2025 |
| Intechstone Limited | Construction | 2012 |
| Integral Alliance | Other services | 2005 |
| Integrated Research UK Limited | Information & communication | 1997 |
| Integrated Webtech Solutions Ltd | Information & communication | 2026 |
| Integration Design 2000 Limited | Wholesale & retail | 1996 |
| Integration Evangelist Limited | Information & communication | 2022 |
| Integridad Assets Ltd | Real estate | 2025 |
| Integrity Employment Solutions Ltd | Administrative & support | 2013 |
| Intelisense Limited | Information & communication | 2015 |
| Intelisync Consulting Limited | Professional & scientific | 2024 |
| Intellectually Limited | Professional & scientific | 2018 |
| Intellidea Advisors Limited | Professional & scientific | 2023 |
| Intelligent Business Rules Ltd. | Information & communication | 2011 |
| Intelligent Cable Monitoring Group Ltd | Manufacturing | 2019 |
| Intelligent Device Loop Consulting Ltd | Professional & scientific | 2016 |
| Intelligent Human Capital Management Limited | Professional & scientific | 2002 |
| Intelligent Marketing Services Ltd | Professional & scientific | 2017 |
| Intelligent Modelling Solutions Limited | Professional & scientific | 2018 |