| Insightiq Software Solutions Ltd | Information & communication | 2024 |
| Insightout Consultancy Ltd | Professional & scientific | 2019 |
| Insignia Creations Limited | Real estate | 2017 |
| Insips Ltd | Manufacturing | 2023 |
| Insley Consultants Limited | Information & communication | 2014 |
| Insomnia Alliance UK Limited | Hospitality | 2015 |
| Insomnia Cafes UK Limited | Hospitality | 2015 |
| Insomnia Coffee House UK Limited | Hospitality | 2016 |
| Inspec Electrical Contractors Ltd | Construction | 2006 |
| Inspirable International Limited | Information & communication | 2019 |
| Inspiration Properties Ltd | Real estate | 2018 |
| Inspirational Youth Development Ltd | Other services | 2022 |
| Inspire ALL Brands Ltd | Arts & recreation | 2026 |
| Inspire Commercial Improvements Ltd | Construction | 2022 |
| Inspire Commercial Ltd | Construction | 2022 |
| Inspire Commercial Renovations Ltd | Construction | 2023 |
| Inspire Design & Home Improvements Ltd | Construction | 2019 |
| Inspire GG Ltd | Construction | 2024 |
| Inspire Home Improvements Ltd | Construction | 2021 |
| Inspire Improvements Ltd | Construction | 2021 |
| Inspire PPS Limited | Administrative & support | 2013 |
| Inspire Renovations Ltd | Construction | 2020 |
| Inspired Commercial Assets Ltd | Real estate | 2026 |
| Inspired Dental Laboratory Ltd. | Administrative & support | 2016 |
| Inspired Foundation Ltd | Health & social care | 2021 |
| Inspired Global Ltd | Professional & scientific | 2024 |
| Inspired Hospitality Management Services Ltd | Hospitality | 2024 |
| Inspired Managed Services Limited | Professional & scientific | 2013 |
| Inspired Management by Design Limited | Construction | 2004 |
| Inspired Marketing and Sales Services Limited | Administrative & support | 2024 |
| Inspiring Creation Limited | Wholesale & retail | 2016 |
| Inspiring Futures Through Learning | Education | 2011 |
| Inspiring Health Solutions Limited | Arts & recreation | 2015 |
| Inspirology Limited | Professional & scientific | 2015 |
| Install Direct (East) Limited | Construction | 2013 |
| Installations Assured Limited | Financial services | 2004 |
| Instant Car Rentals Limited | Administrative & support | 2010 |
| Instant Doors Limited | Wholesale & retail | 2001 |
| Instant GP Limited | Health & social care | 2024 |
| Instant Watch Buyer Ltd | Wholesale & retail | 2024 |
| Instant Workforce (MK) Limited | Administrative & support | 2025 |
| Instant Workforce Limited | Administrative & support | 2019 |
| Instantk Ltd | Other services | 2024 |
| Instaweb Ltd | Information & communication | 2012 |
| Instinctive Group Holdings Limited | Financial services | 2011 |
| Instinctive Limited | Manufacturing | 1991 |
| Institute of Acoustics Limited (the) | Other services | 1974 |
| Institute of Automotive Engineer Assessors (the) | Other services | 1939 |
| Institute of Internal Communication Limited | Other services | 1963 |
| Institute of Translation and Interpreting | Other services | 1987 |
| Insurance Database Services Limited | Professional & scientific | 1993 |
| Insurance Fraud Bureau | Other services | 2012 |
| Insurelectric Limited | Construction | 2020 |
| Insuriva Ltd | Financial services | 2010 |
| Insuvia Guard Limited | Construction | 2025 |
| Insync Interiors and Designs Ltd | Construction | 2019 |
| Intec Printing Solutions Limited | Manufacturing | 1995 |
| Integer Property Ltd | Real estate | 2018 |
| INTEGR8 Communications Limited | Professional & scientific | 2006 |
| Integral Energy (Inc) Limited | Mining & quarrying | 2021 |
| Integral Powertrain Limited | Manufacturing | 1998 |
| Integrals Power Limited | Manufacturing | 2020 |
| Integrate Finance Ltd | Professional & scientific | 2025 |
| Integrated Bird Management Limited | Administrative & support | 2024 |
| Integrated Care Associates Ltd | Professional & scientific | 2018 |
| Integrated Full Electric Propulsion Collaboration Ltd | Manufacturing | 2025 |
| Integrated Medical Solutions Limited | Administrative & support | 1995 |
| Integrated Planning Support Limited | Other services | 2008 |
| Integrity Corporation Limited | Administrative & support | 2011 |
| Integrity Supported Living Ltd | Health & social care | 2022 |
| Integrity Technology Consulting and Services Limited | Information & communication | 2008 |
| Integrityinvest Realty Ltd | Real estate | 2025 |
| Integro Cloud Ltd | Information & communication | 2022 |
| Integrum Training & Consultancy Ltd | Health & social care | 2023 |
| Inteli Works Limited | Information & communication | 2021 |
| Intelidat Limited | Information & communication | 2021 |
| Intellect Technologies Ltd | Information & communication | 2023 |
| Intellectica Ltd | Wholesale & retail | 2012 |
| Intelli EV Ltd | Wholesale & retail | 2018 |
| Intelli Nova Ltd | Professional & scientific | 2025 |
| Intellifinds Limited | Professional & scientific | 2019 |
| Intelligent Conversions Ltd | Construction | 2009 |
| Intelligent Employment Limited | Administrative & support | 2006 |
| Intelligent Finance Solutions Limited | Financial services | 2008 |
| Intelligent Financial Advice Ltd | Financial services | 2003 |
| Intelligent Financial Advice Services Limited | Administrative & support | 2009 |
| Intelligent Interface Company Ltd | Information & communication | 2025 |
| Intelligent Logistics Ltd | Transport & logistics | 2016 |
| Intelligent Maintenance Systems Limited | Information & communication | 2000 |
| Intelligent Processing Solutions Limited | Financial services | 2000 |
| Intelligent Talk Ltd | Administrative & support | 2010 |
| Intelligent Timing Ltd | Information & communication | 2025 |
| Intelligent Wealth Limited | Financial services | 2015 |
| Intelligent Wealth Solutions Limited | Financial services | 2005 |
| Intelligentsia Inc Limited | Information & communication | 2012 |
| Intellipartners Consulting Limited | Professional & scientific | 2024 |
| Intellisense Solutions Ltd | Information & communication | 2019 |
| Intelog Ltd | Professional & scientific | 2024 |
| Intenseflow Ltd | Other services | 2023 |
| Inter County Care Ltd | Health & social care | 2025 |