| Idem Safety Switches LimitedWigan, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2003 |
| Iforce LtdWarrington, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1997 |
| Ikou LimitedNorth Shields, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2025 |
| Il-Uk Fresh Produce LimitedHarrow, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2011 |
| Imagination Technologies LimitedKings Langley, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1977 |
| Imagine Capital LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2017 |
| Impact Xm Europe LtdLeatherhead, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2009 |
| Imperial Treasure Co., LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2016 |
| Inaparc LtdAlcester, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2009 |
| Inbrit Logistics LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1995 |
| Indie Brands LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2011 |
| Indimart Food & Beverages LimitedMilton Keynes, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2022 |
| Inflexion Private Equity Partners LLPLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2005 |
| Innerworkings Europe LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1984 |
| International Plywood LtdStonehouse, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1981 |
| International Wine LimitedIlkley, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2020 |
| Intocast UK LtdRotherham, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2003 |
| Intrepid Wines LtdShepton Mallet, United Kingdom · UKintrepidwines.com · checked 28 Oct 2026 | UK | 1 | – | – | –Value (producers) | 0% | 2025 |
| Intriva Services LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2016 |
| Invivo Wines UK LtdKettering, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2018 |
| Ipl LtdDudley, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1997 |
| Iq Eq Administration Service S LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2014 |
| Isometrix Lighting &DESIGN LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1992 |
| Italia Wine and Food LtdUnited Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2018 |
| Italian Food Holding LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2021 |
| Italtaste LimitedWoking, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2010 |
| Iveria Wines LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2025 |
| J & C Omeara LtdBurscough, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1990 |
| J & de LtdMarket Harborough, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2017 |
| J A Rose LtdMacclesfield, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2009 |
| J Chandler & Co LtdAndover, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1927 |
| J D Wetherspoon PLCWatford, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1983 |
| J V International LtdWilmslow, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2006 |
| J&B Selections LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2025 |
| J. Davidson Scrap Metal Proc Essors LimitedAltrincham, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2011 |
| J.c. Bamford Excavators LimitedUttoxeter, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1956 |
| Jab Partners LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2021 |
| Jack Nadel International LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2000 |
| Jacquart UK LimitedLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2024 |
| Jakmob International LimitedCroydon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2012 |
| Jaks Bars & Restaurants LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2010 |
| James Boylan Safety LtdOmagh, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1958 |
| Jane Street Europe LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2006 |
| Jazz Pharmaceuticals UK LtdLondon, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2002 |
| Jba Corporation LtdPrinces Risborough, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2017 |
| Jellysmack LimitedWyboston, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2020 |
| Jenner and Block London LLPNew Castle, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2023 |
| Jenny Beavan Designs LimitedWorthing, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2004 |
| Jetvine Consultancy LtdWalton-on-Thames, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 2020 |
| Jfc LimitedHayes, United Kingdom · UKchecked 28 Oct 2026 | UK | 1 | – | – | – | – | 1992 |