| Inovitec Limited | Malpas | 1997 |
| Input IT Ltd | Leeds | 2003 |
| Insecta Nova Ltd | Wallington | 2025 |
| Insemigen Ltd | Bristol | 2023 |
| Inserotech Limited | Sandwich | 2007 |
| Inshewan Salmon Fishing Limited | Broughty Ferry | 2026 |
| Inshore Fishing Ltd | Glasgow | 2004 |
| Insider Mart Limited | Essex | 2024 |
| Insieme Kent Ltd | Eastbourne | 2025 |
| Insight Marine Ltd | Glasgow | 2024 |
| Insignia Property Maintenance Services Limited | London | 2025 |
| Insite Farms UK Ltd | Immingham | 2020 |
| Inspirational Teaching Limited | Bromley | 2018 |
| Inspired Renovations Swanwick Limited | Knutsford | 2008 |
| Instant Timber Limited | Bampton | 1998 |
| Institute of Auctioneers and Appraisers in Scotland. | Edinburgh | 1926 |
| Insycle Protein Ltd | Craven Arms | 2021 |
| Integrated ARB Solutions Limited | Stockton On Tees | 2022 |
| Integrated Crop Advice Ltd | Denton | 2000 |
| Integrated Crop Management (SW) Limited | Cambridge | 1999 |
| Intelgenic Ltd | Coventry | 2021 |
| Intelifish Ltd | London | 2026 |
| Intelligent Agriculture Limited | Stonehouse | 2009 |
| Intelligent Fruit Ltd | West Malling | 2012 |
| Intelligrow Agriculture Ltd | Woking | 2021 |
| Intellinavix Limited | Glasgow | 2023 |
| Inter K9 Imports Ltd | Dereham | 2020 |
| Intercrop Limited | Deal | 1991 |
| Interface NRM Limited | Telford | 2002 |
| Interfish Producer Organisation Limited | Plymouth | 2008 |
| Interforth Limited | Ross Shire | 1994 |
| Intergrate Ltd | Okehampton | 2005 |
| Interlawn Ltd | York | 2024 |
| International Adventures Farming Ltd | Kirriemuir | 2023 |
| International Animals Protection Association | London | 2023 |
| International Big Game & Bird Hunting Ltd | Grangemouth | 2015 |
| International Cocoa Diplomacy | London | 2020 |
| International Energy Crops Limited | Market Drayton | 2009 |
| International Horse Imports Limited | Reading | 2025 |
| International Maritime Services Limited | Dorking | 1997 |
| International Mass Private Limited | Birmingham | 2025 |
| International Medical Foods Limited | London | 2017 |
| International Parrot Rescue Ltd | London | 2018 |
| International Pome Fruit Alliance Limited | London | 2010 |
| International Sport Horses Limited | St. Andrews | 2018 |
| International Sporting Falcons Limited | Rotherham | 2018 |
| International Wildlife Consultants (UK) Limited | Carmarthen | 2006 |
| International Wool Harvesters CIC | Bristol | 2024 |
| Interoperability Services Limited | Brackenfield Alfreton | 2003 |
| Intersea Food Scotland Limited | Munlochy | 2014 |
| Interveg Limited | Huntingdon | 2000 |
| Into the Great Wide Open Limited | Matlock | 2022 |
| Intravita International Limited | Tiptree | 2014 |
| Intrinsic Business Services Limited | Clyst St Mary | 1998 |
| Intsol Limited | Barnstaple | 2007 |
| Invasive Weed Management Ltd | Leeds | 2014 |
| Invasix Tree & Land Control Ltd | Lochgilphead | 2026 |
| Inventys Land Ltd | Grantown On Spey | 2018 |
| Inveran Fishing Limited | Oban | 2011 |
| Inverarity Farms Limited | Dundee | 1945 |
| Inverawe Estates Limited | Taynuilt | 2007 |
| Invercannich Farm Limited | Beauly | 2025 |
| Inverdrill Limited | Tain | 1997 |
| Inverfish Limited | Peterhead | 2020 |
| Inverlael Ventures Ltd | Garve | 2021 |
| Inverlussa Shellfish Company Limited | Isle Of Mull | 2004 |
| Inverlussa Shipping Co Limited | Isle Of Mull | 2023 |
| Invermarkie Farms Ltd | Turriff | 2020 |
| Inverness Tree Services Ltd. | By Dingwall | 2004 |
| Inverquhomery Farm Limited | Aberdeenshire | 1995 |
| Invert Your World Limited | Durham | 2026 |
| Inverugie Blue Leader Ltd. | Shetland | 2008 |
| Inverugie Mains Limited | Aberdeenshire | 1950 |
| Inverurie Farm Consultancy Ltd. | Huntly | 2007 |
| Investfront Farms Limited | Reading | 2021 |
| Invicta Trout Limited | Dumfries | 1972 |
| Invictus Nova Ltd | Borehamwood | 2019 |
| Inwood Forestry Ltd | Farnham | 2020 |
| Iolo Davies CYF | Pwllheli | 2026 |
| Iolo Owen & Co. Limited | Bodorgan | 1974 |
| Iona Seafood Ltd | Isle Of Iona | 2020 |
| IPA Fishing Limited | Teignmouth | 1990 |
| IPJ Ltd | Hereford | 2023 |
| Ipley Manor Farm Limited | Marchwood | 1991 |
| IPM Perth Limited | Angus | 1989 |
| Ipswich Firewood Ltd | Ipswich | 2022 |
| IQ Eggs Limited | Stevenage | 2009 |
| Irchester Lakes Limited | Wickford | 2017 |
| Irco Mena Ltd | Craven Arms | 2010 |
| Ireland Prods. Limited | Grantham | 2022 |
| Irelands' Farms Limited | Sleaford | 1996 |
| Ireosa Limited | Dorchester | 1981 |
| Irfon Davies Limited | Haverfordwest | 2002 |
| Irie Foods Ltd | Wallington | 2023 |
| Iris (Eco) Ltd | Derby | 2021 |
| Iris Farm Agroforestry Ltd | Glastonbury | 2024 |
| Iris Produce Limited | Melton Mowbray | 2022 |
| Irish Cattle Breeding Centre (UK) Limited | London | 2014 |
| Irish Hemp Ltd | Armagh | 2021 |
| Irish Moiled Cattle Society | Ballymena | 1998 |