| Instant Lessons Ltd | Bristol | 2023 |
| Instant Opera Limited | Teddington | 2017 |
| Instant Services (Scotland) Ltd | Glasgow | 2022 |
| Instant Swim School Ltd | Aylesford | 2021 |
| Instant Upskill Ltd | Ryehill | 2020 |
| Instanter Learning Trust | Sunbury-On-Thames | 2012 |
| Instanttutor Ltd | Ruislip, | 2023 |
| Instar Coaching C.I.C. | Southampton | 2017 |
| Instar Education Group Ltd | London | 2022 |
| Instepz Limited | Birmingham | 2007 |
| Instigate Unknown Ltd | Essex | 2019 |
| Instill Education Limited | Oxford | 1977 |
| Instillexcellence Ltd | Stourbridge | 2013 |
| Instinct AI Ltd | Exeter | 2014 |
| Instinct Anatomy Life Ltd | Harrow | 2021 |
| Instinct Boxing and Fitness Limited | Taunton | 2022 |
| Instinct Business Services Ltd | Long Eaton | 2015 |
| Instinctive Resilience Ltd | London | 2024 |
| Instinctive Thinking Ltd | Hindhead | 2024 |
| Instincts Training Ltd | Rotherham | 2022 |
| Instinctual Acting for Camera Limited | London | 2023 |
| Institut Alif LEM Ltd | London | 2023 |
| Institute and Faculty Education Limited | London | 1995 |
| Institute for Business Development in Euro Asia Limited | Chester Le Street | 1993 |
| Institute for Children, Youth and Mission | Canterbury | 2000 |
| Institute for Continuous Improvement in Public Services | Driffield | 2012 |
| Institute for European Environmental Policy, London | London | 1990 |
| Institute for Health Economics and Outcomes Research Limited | Oxford | 2014 |
| Institute for Independent Business-International Limited | Chesham | 2003 |
| Institute for Polish-Jewish Studies(The) | London | 1986 |
| Institute for the Future of Work | London | 2018 |
| Institute of Advanced Motorists Limited(The) | Welwyn Garden City | 1956 |
| Institute of Animal Technology(The) | Oxford | 1965 |
| Institute of Art - London Limited | London | 1995 |
| Institute of Biodynamic Medicine Limited | Staines-Upon-Thames | 1989 |
| Institute of British Sign Language | Cardiff | 2007 |
| Institute of Business Ethics | London | 2018 |
| Institute of Chartered Accountants of Nigeria - UK and District Society | London | 2026 |
| Institute of Commerce Limited(The) | High Wycombe | 1908 |
| Institute of Corporate Resilience (Iocr) Limited | Colchester | 2021 |
| Institute of Data and Marketing Limited | London | 1987 |
| Institute of Data Ltd | Belfast | 2023 |
| Institute of Detectorists C.I.C. | Kington | 2018 |
| Institute of Family Therapy | London | 1982 |
| Institute of Imagination | London | 2003 |
| Institute of Jainology Limited | Stanmore | 2008 |
| Institute of Legacy Management | Dorking | 2001 |
| Institute of Linguists(The) | Rochester | 1958 |
| Institute of Masters of Wine(The) | London | 1972 |
| Institute of Payroll Professionals | Solihull | 1997 |
| Institute of Professional Development Limited | Hyde | 2024 |
| Institute of Race Relations(The) | London | 1958 |
| Institute of Retail Distribution Management | Blackpool | 1962 |
| Institute of Risk Management | London | 1986 |
| Institute of School Business Leadership | Leamington Spa | 1997 |
| Institute of Small Business Management | London | 1998 |
| Institute of ST. Anselm(The) | Margate | 1986 |
| Institute of Strategic Risk Management Limited | London | 2018 |
| Institute of the Horse | Kenilworth | 1999 |
| Institution of Fire Engineers (the) | Edinburgh | 1924 |
| Instituto Brasileiro DE Ensino Labrayon EM Londres Ltd | London | 2015 |
| Instituto Du'Rose Ltd | London | 2026 |
| Instrucko Limited | London | 2020 |
| Instruckt Ltd | Teignmouth | 2022 |
| Instrucom Ltd | London | 2018 |
| Instruct IQ Ltd | Hereford | 2025 |
| Instruct ME Limited | Salford | 2025 |
| Instructed to Independent Ltd | London | 2025 |
| Instructional Design Services Ltd | Romford | 2016 |
| Instructor & Examiner Academy Ltd | Cardiff | 2019 |
| Instructor College UK Ltd | Bristol | 2022 |
| Instructor MAX Ltd | Caldicot | 2023 |
| Instructor Nathan Limited | Northampton | 2025 |
| Instructor Standard Authority Ltd | West Midlands | 2015 |
| Instructors Direct Ltd | Manchester | 2024 |
| Instructr Ltd | London | 2025 |
| Instructus | Market Harborough | 2009 |
| Instrumental Arts Ltd | Norwich | 2026 |
| Instrumental Health Community Services CIC | London | 2026 |
| Instrumental Lessons With Emily Ltd | London | 2024 |
| Instrumental Living Academy Ltd | Portsmouth | 2023 |
| Instrumental Music Services Limited | Exeter | 2003 |
| Instruments of Cognition Ltd | London | 2022 |
| Instudents Ltd | Birmingham | 2023 |
| Instustock Ltd | London | 2019 |
| Insulation Environmental Training Trust Limited | Darlington | 1991 |
| Insync Glasgow CIC | Glasgow | 2025 |
| Insync Global Education Ltd. | Harrogate | 2013 |
| INT Programs Group Ltd | London | 2021 |
| Int-Se Ltd | Sleaford | 2021 |
| Intack International Ltd. | Withernsea | 1999 |
| Intact London Ltd | London | 2019 |
| Intake Pre-School | Sheffield | 2004 |
| Intapsych Ltd. | Winchester | 2008 |
| Intara Ltd | Tonbridge | 2025 |
| Intbusiness Limited | Ilford | 2013 |
| Intec Business Colleges Limited | Rugby | 1990 |
| Intec Education Ltd | Sutton | 2012 |
| Inteducation Ltd | Wembley | 2016 |
| Integ Academy Ltd | Liverpool | 2024 |