| International Sport Mental Coaching Ltd | London | 2015 |
| International Sports Engineering Association | Nottingham | 2017 |
| International Sports Sciences College Ltd | London | 2024 |
| International Stem Cell Biobanking Initiative | Royston | 2023 |
| International Student Club Limited | Penarth | 1997 |
| International Student Consultations Ltd | London | 2026 |
| International Student Experiences Ltd | London | 2024 |
| International Student Gateway Ltd | London | 2025 |
| International Student Guardianship & Education Services Limited | Cardiff | 2020 |
| International Student Network Ltd | Aylesford | 2025 |
| International Student Services CS Ltd | Hayes | 2016 |
| International Students Advisory Limited | London | 2023 |
| International Students Agent Limited | Bournemouth | 2019 |
| International Students Services Ltd | Bournemouth | 2021 |
| International Students Unity | Nottingham | 2025 |
| International Study and Exchange Consult Ltd | Enfield | 2024 |
| International Study Centre UK Limited | Rochester | 2018 |
| International Study Programmes Limited | Norwich | 1982 |
| International Study Solutions Limited | Manchester | 2016 |
| International Subscription Agency Ltd | London | 2025 |
| International Summer Camp UK Ltd | Bridge Of Weir | 2011 |
| International Summer School for Teens Limited | London | 2015 |
| International Sustainable Development Research Society Limited | Chesterfield | 2026 |
| International Swimming Academy Ltd | Kington | 2016 |
| International Swimming Academy Stars Limited | Kington | 2016 |
| International Syndicate of Health and Aesthetic Services Workers and Psychotherapists and Special Education Specialists Ltd | Leicester | 2026 |
| International Taekwon-Do Federation Limited | Swindon | 2009 |
| International Tartans CIC | Eyemouth | 2025 |
| International Teachers College [ITC] London Limited | London | 2018 |
| International Teachers Ltd | Bristol | 2024 |
| International Teaching Learning Assessment Consultants and Online Schools Limited | Leeds | 2024 |
| International Teaching Seminars Ltd | Wotton-Under-Edge | 2015 |
| International Technology Assisted Wellness & Beauty Training Centre Ltd | Manchester | 2025 |
| International Test Limited | London | 2023 |
| International Testing and Evaluation Service Limited | Manchester | 2022 |
| International Thai Foundation Ltd | Warrington | 2010 |
| International Theatre Exchange | London | 1992 |
| International Training & Development Ltd | London | 2017 |
| International Training & Qualifications Ltd | Warrington | 2025 |
| International Training Centre London Limited | London | 2017 |
| International Training College Ltd | Netherfield | 2021 |
| International Training Leaders Academy Ltd | Manchester | 2025 |
| International Treasury Services (Europe) Limited | Faversham | 2010 |
| International UNI of London Ltd | Nottingham | 2026 |
| International Union for Press and Media Ltd | London | 2024 |
| International Union of Academics, Researchers and Specialized Trainers Ltd | Cardiff | 2025 |
| International Union of Arbitrators London Ltd | London | 2025 |
| International Union of Professional Trainers Ltd | Nottingham | 2021 |
| International Urology Cancer Summit C.I.C. | Havant | 2026 |
| International Vegetarian Union | Manchester | 2001 |
| International Village Education Limited | Gloucester | 2015 |
| International Vocational Qualification Ltd | Scotland | 2025 |
| International Warrior Academy Ltd | Birmingham | 2025 |
| International Wildlife Coalition Trust | Kent | 1991 |
| International Women of Substance Limited | London | 2015 |
| International Yachtmaster Training Ltd | London | 2019 |
| International Youth Federation | London | 2017 |
| International Youth Speaking Festival Ltd | Slough | 2026 |
| International Youth Sports Centre Ltd | Croydon | 2024 |
| Internet Education Academy Ltd | Preston | 2024 |
| Internet English Classes Ltd | London | 2015 |
| Internet of Things Academy Ltd | Mansfield | 2016 |
| Internity.Life Ltd | Dorking | 2019 |
| Internoutreach Ltd | Manchester | 2026 |
| Internplacements Limited | London | 2013 |
| Interoception International Ltd | Trowbridge | 2025 |
| Interp-Ability Limited | Tunbridge Wells | 2013 |
| Interpreter Ltd | London | 2022 |
| Interpreters of Colour Network Community Interest Company | London | 2020 |
| Interre Concepts Ltd | Dagenham | 2023 |
| Interrupt.Digital Ltd | Chester | 2009 |
| Intersect Education Ltd | Nottingham | 2024 |
| Intersectional Psychology Ltd | London | 2022 |
| Intersectionality Womens Programmes CIC | Bedford | 2023 |
| Intersphere Educational Services Limited | Edinburgh | 2017 |
| Interstellar Academy Limited | Leicester | 2019 |
| Interstellar Learning Solutions Limited | Dundee | 2022 |
| Intersticia UK | London | 2018 |
| Interstu Limited | London | 2016 |
| Interstudies London Ltd | Twickenham | 2014 |
| Interstudies Ltd | London | 2002 |
| Intertalent Louder Foundation Ltd | London | 2013 |
| Intertidal LAB CIC | Stroud | 2025 |
| Intertrain UK Ltd. | Doncaster | 2003 |
| Intertwined Ltd | London | 2024 |
| Intervention Academy Ltd | Wigan | 2024 |
| Intervention Academy Tutoring Ltd | Wigan | 2025 |
| Intervention First Ltd | Congleton | 2025 |
| Intervention Initiatives CIC | London | 2024 |
| Interview & YOU Ltd | Walton-On-Thames | 2024 |
| Interview Art UK Limited | Formby | 2025 |
| Interview DOC Ltd | London | 2025 |
| Interview IQ Limited | Thornton Heath | 2025 |
| Interview Playbook Limited | Sevenoaks | 2025 |
| Interview Rookie Ltd | Brackley | 2025 |
| Interview Skills Academy Ltd | Slough | 2016 |
| Interwood Football Club CIC | London | 2022 |
| Interworking Ltd | Glossop | 2026 |
| Intesol Worldwide Limited | Wells | 2006 |
| Intevario Ltd | London | 2025 |