| Inventors League Ltd | London | 2026 |
| Inverclyde Darts Hub C.I.C. | Port Glasgow | 2026 |
| Inverdart Consultancy Ltd | Dartmouth | 2020 |
| Inversion Academy Ltd | Torrington | 2025 |
| Inversity Ltd | London | 2022 |
| Inverted Diamond Ltd | Lochgelly | 2025 |
| Inverted State of Mind Limited | London | 2024 |
| Invest Ahead Limited | Bath | 2026 |
| Invest Education Ltd | Ormskirk | 2025 |
| Invest in Learning Limited | Solihull | 2012 |
| Invest in Nature C.I.C. | Bishop Auckland | 2024 |
| Invest in Play Ltd | Brimstage Road | 2022 |
| Invest in Skills People Limited | Chesterfield | 2008 |
| Invest in YOU Coaching Ltd | Marlborough | 2023 |
| Invest in Yourself Youth Services Limited | Grays | 2018 |
| Invest Learning Management T/A ILM Ltd | Holborn | 2024 |
| Invest Station Group Ltd | Mildenhall | 2025 |
| Invest Training Limited | Newton Aycliffe | 2023 |
| Investavimas Visiems Ltd | Gravesend | 2025 |
| Invested Education Ltd | Redcar | 2021 |
| Investigate 2 Educate CIC | Billericay | 2025 |
| Investin Education Limited | London | 2012 |
| Investing Earning Living Ltd | Blackpool | 2020 |
| Investing in Education Ltd | London | 2018 |
| Investing in the People of Tomorrow Ltd | Fairford | 2020 |
| Investinu Academy Ltd | London | 2020 |
| Investment Box Limited | Newton Aycliffe | 2017 |
| Investment Education Ltd | Salford | 1987 |
| Investment Mastery Trading Limited | London | 2014 |
| Investment Success BEN Academy Ltd | London | 2018 |
| Investmentor.Club Limited | Wellingborough | 2025 |
| Investor in Careers Ltd | London | 2024 |
| Investoregulation Limited | London | 2004 |
| Investors for Change Ltd | Stoke-On-Trent | 2024 |
| Investorsinuniversities Limited | Salcombe | 2017 |
| Investorsocean Ltd | London | 2017 |
| Invicta Community Leisure CIC | Herne Bay | 2023 |
| Invicta Education Consulting Ltd | Walsall | 2023 |
| Invicta Education, Training and Consulting Limited | London | 2015 |
| Invicta Strategic Consultants Ltd | London | 2026 |
| Invicta Training Limited | Sittingbourne | 2016 |
| Invictus Development Center CIC | London | 2025 |
| Invictus Education Trust | Kinver | 2014 |
| Invictus Gymnastics Club Limited | Tadley | 2021 |
| Invictus Professional Training Ltd | Portsmouth | 2017 |
| Invictus Sales & Leadership Solutions Ltd | Glasgow | 2024 |
| Invictus School of Computer & Technology Ltd | London | 2025 |
| Invictus Therapy Ltd | Scunthorpe | 2020 |
| Invictus Training Solutions Ltd | Warwickshire | 2006 |
| Inview AI Ltd | London | 2025 |
| Inview VR C.I.C. | London | 2024 |
| Invigilating Service for Best Independent Schools Limited | Hastings | 2025 |
| Invigorate Education Ltd | Croydon | 2020 |
| Invincible Voices Ltd | London | 2013 |
| Invirtigo Ltd | Westcliff-On-Sea | 2021 |
| Invis-Ability C.I.C. | Stevenage | 2018 |
| Invisible Communications Limited | Newark | 1993 |
| Invisible Grail Limited | Yelverton | 2017 |
| Invisible Skate Tribe Ltd | Liverpool | 2024 |
| Invisible to In-Demand Ltd | London | 2023 |
| Invitation to Inclusion CIC | Chipping Campden | 2026 |
| Invoke Dance and Wellness Ltd | Stourbridge | 2024 |
| Invol Education Ltd | Eastleigh | 2025 |
| Involv Productions CIC | Glasgow | 2026 |
| Involve Active Ltd | Lowestoft | 2012 |
| Involve Leeds | Leeds | 2015 |
| Involve Razem Community Interest Company | Thetford | 2016 |
| Involved and Equal CIC | Gateshead | 2022 |
| Involved Fathers CIC | London | 2021 |
| Involved Learning Limited | Bury | 2012 |
| Involved Social Impact Projects Limited | Leeds | 2018 |
| Involver Education Ltd | London | 2009 |
| Involving Residents in Solutions Ltd | Bristol | 2000 |
| Inwood Nursery Limited | Weston-Super-Mare | 2011 |
| Inyoni Ltd | Beckenham | 2024 |
| INZ Informa Ltd | Glasgow | 2024 |
| Inzite Solutions Limited | Romford | 2023 |
| IO Connect Ltd | Chesterfield | 2025 |
| IO Education Services Limited | Blandford Forum | 2021 |
| IO Sphere Limited | London | 2022 |
| IO3-E Int’L Ltd | London | 2023 |
| Ioai Global Ltd | Portsmouth | 2025 |
| IOC Global Limited | London | 2012 |
| IOC Tutors Limited | Reading | 2025 |
| Iodc Limited | | 1996 |
| Ioee International Ltd | Darlington | 2025 |
| Ioex Ltd | Lynch Wood, Peterborough | 1977 |
| IOI Consulting Ltd | Twickenham | 2013 |
| IOI Enterprise Ltd | London | 2017 |
| IOL Educational Trust | Rochester | 2001 |
| Iolt Limited | Woodford Green | 2013 |
| Ion's Driving School Limited | Northampton | 2013 |
| Ion-D Limited | London | 2021 |
| Iona Nursery Limited | Peterculter | 2011 |
| Iona School Association | Brighton | 1985 |
| Ionad Chaluim Chille ILE | Isle Of Islay | 2000 |
| Ionad Gàidhlig an T Sàilein C.I.C. | Glasgow | 2026 |
| Ioncloud Ltd | Ilford | 2025 |
| Iopc Ltd | Settle | 2018 |
| Iopener Limited | Banbury | 2003 |