| Trade OFF Events Ltd | Wholesale & retail | 2026 |
| Traditio Limited | Transport & logistics | 2024 |
| Trapex Limited | Manufacturing | 2016 |
| Treacy Plant Hire Limited | Construction | 1967 |
| Treegull Ltd | Other services | 2016 |
| Trelmco Limited | Professional & scientific | 2004 |
| Trinity Portfolio Ltd | Construction | 2004 |
| Trouble & Desire Films Limited | Information & communication | 2010 |
| Trueline Limited | | 1984 |
| Tuesdayadams Limited | Professional & scientific | 2002 |
| Tuono Tech Services Ltd | Construction | 2022 |
| Turners Hill Registrars Limited | Other services | 2002 |
| Turtle Developments Ltd | Construction | 2025 |
| Two White Bears Ltd | Wholesale & retail | 2019 |
| Tyre 'N' Tube Choice Limited | Wholesale & retail | 2009 |
| U.G. Containers Limited | Professional & scientific | 1925 |
| UH Ventures Limited | Education | 1989 |
| UK Landmark Holdings Ltd | Real estate | 2018 |
| Ultimatecoach Ltd | Information & communication | 2006 |
| Upper Brook Street RTM Company Limited | Households | 2005 |
| Urban Bliss Limited | Other services | 2003 |
| V & F Giddings Property Maintenance Limited | Construction | 2003 |
| Value Alpha Limited | Professional & scientific | 2006 |
| Vanscare Limited | Health & social care | 2015 |
| Vardons Solutions Limited | Financial services | 2023 |
| Varis Holdings Ltd | Administrative & support | 2020 |
| Varis Leisure Borehamwood Ltd | Arts & recreation | 2020 |
| Varis SIA Limited | Administrative & support | 2020 |
| Vast Life (UK) Limited | Wholesale & retail | 2005 |
| Vector Construction Limited | Wholesale & retail | 1996 |
| Vertica Technology Limited | Information & communication | 2007 |
| Viewscope Limited | Professional & scientific | 1989 |
| Virtual Sensory Perception | | 1998 |
| Volkerfitzpatrick Limited | Construction | 1989 |
| W & H (UK) Limited | Manufacturing | 1991 |
| W.J. Dickinson & Sons (Farmers) Limited | Agriculture & fishing | 1942 |
| W.J. Murray & SON Limited | Other services | 1988 |
| Wade Diesels Limited | Wholesale & retail | 1983 |
| Walton Homes (UK) Limited | Construction | 2007 |
| Watford Specsavers Limited | Wholesale & retail | 1994 |
| Watford Visionplus Limited | Wholesale & retail | 1994 |
| Watling Commercial Rentals Ltd | Real estate | 1946 |
| WE GOT YOU Boutique Ltd | Wholesale & retail | 2024 |
| Webcentric Ltd | Information & communication | 2006 |
| Welcome Homes Limited | Construction | 1996 |
| Well Road Ltd | Households | 2020 |
| Wellbeing and Development Centre Ltd | Health & social care | 2023 |
| Welwyn Services Limited | Water & waste | 2007 |
| West IT Limited | Information & communication | 2007 |
| Westminster Waste Limited | Water & waste | 2010 |
| WGF Suppliers Ltd | Wholesale & retail | 2015 |
| Whisky Records Limited | Administrative & support | 2007 |
| White Contracting Limited | Transport & logistics | 2007 |
| Wilden Services Limited | Construction | 1973 |
| Will Paterson Limited | Professional & scientific | 2013 |
| Williams & Firth | | 2000 |
| Winningcroft Limited | | 1978 |
| Winyates Property Investment Limited | Real estate | 2003 |
| Wireplace Limited | | 1990 |
| WM. Nagle & Company Limited | Real estate | 1979 |
| Woodbe Joinery Ltd | Construction | 2014 |
| Woodland Investments Limited | Real estate | 2000 |
| Woodtown Ltd | Construction | 2013 |
| Words ETC Limited | Information & communication | 2001 |
| Wordsmith Features Limited | Arts & recreation | 2003 |
| World Wide Advent Missions Limited | Other services | 1929 |
| Wrapid Packaging Solutions Limited | Professional & scientific | 2007 |
| Wraplas Limited | Other services | 2007 |
| WWL Limited | Financial services | 2015 |
| YEW Tree Farm Trading Limited | Professional & scientific | 2007 |
| YHR Holdings Ltd | Real estate | 2026 |
| YIN Yang Enterprises Limited | Information & communication | 2006 |
| Yokegraph Limited | | 1985 |
| Zandra Limited | Real estate | 2006 |
| Zeroland Limited | | 1982 |
| Zeroninemx Limited | Manufacturing | 2006 |
| Zion Audio Limited | Information & communication | 2015 |