| Gray's Inn Investments Limited | Real estate | 1995 |
| Gray's Inn Realty Limited | Real estate | 2005 |
| Grays Lincoln Ltd | Health & social care | 2026 |
| Grays Medica Ltd | Health & social care | 2024 |
| Grazing Girls Ltd | Hospitality | 2020 |
| GRE Ventures Ltd | Information & communication | 2026 |
| Great Day Properties Limited | Real estate | 2025 |
| Great Oak Professional Services Limited | Information & communication | 2006 |
| Great Western Wine Company Limited(The) | Wholesale & retail | 1983 |
| Greek Time Ltd | Hospitality | 2024 |
| Green and Life Gardening Ltd | Professional & scientific | 2026 |
| Green and Red Properties Limited | Real estate | 2021 |
| Green Array and Threads Ltd | Wholesale & retail | 2026 |
| Green Balls Ltd | Wholesale & retail | 2023 |
| Green Channel (GB) Limited | Information & communication | 2005 |
| Green Developers Limited | Construction | 2020 |
| Green Energy Capital Investment Ltd. | Wholesale & retail | 2011 |
| Green Frog Car Wash Ltd | Wholesale & retail | 2021 |
| Green Leaf IT Ltd | Wholesale & retail | 2026 |
| Green Legal Agents Limited | Administrative & support | 2015 |
| Green Life Landscapes Limited | Construction | 2019 |
| Green Merlin Limited | Real estate | 2025 |
| Green Resource Recycling (GRR) Ltd | Water & waste | 2007 |
| Green Tree Consulting Ltd | Professional & scientific | 2023 |
| Greenbridge Solutions Limited | Information & communication | 2025 |
| Greenbury Construction Ltd | Construction | 2019 |
| Greenchime Property Management Limited | Households | 1989 |
| Greencube Services Limited | Other services | 2016 |
| Greene Square Ltd | Wholesale & retail | 2020 |
| Greeneffort Marketing Ltd | Professional & scientific | 2011 |
| Greener Future Property Services Limited | Construction | 2024 |
| Greener Property Solutions Limited | Real estate | 2023 |
| Greenfield Drive RES. Assoc. (Fortis Green) Limited | Households | 1996 |
| Greenfield Project Consulting Limited | Professional & scientific | 2010 |
| Greenhill Mansions (Management) Co. Limited | Administrative & support | 1965 |
| Greenhill Mansions Freehold Limited | Real estate | 2001 |
| Greenhurst Homes Limited | Construction | 2018 |
| Greenidge Farm Ltd | Agriculture & fishing | 2013 |
| Greenight Personnel Ltd | Construction | 2017 |
| Greenlight Assets Limited | Real estate | 2024 |
| Greenlight Medicare Ltd | Wholesale & retail | 2019 |
| Greenlink Express Limited | Transport & logistics | 2012 |
| Greenlowe Property Company Limited | Administrative & support | 1993 |
| Greenstone Estates Management Limited | Administrative & support | 2015 |
| Greensward Sports Consultancy Ltd | Administrative & support | 2012 |
| Greentropy Limited | Professional & scientific | 2024 |
| Greenwich 2000 Limited | Information & communication | 1996 |
| Greenwize Ltd | Wholesale & retail | 2020 |
| Greg & Bros Ltd | Construction | 2016 |
| Gregs Team Ltd | Construction | 2024 |
| Gresha Limited | Professional & scientific | 2020 |
| Gresser Business Solutions Ltd | Information & communication | 2020 |
| Greswolde Construction Limited | Construction | 1983 |
| Grey Dove Ltd | Administrative & support | 2008 |
| Grey House Consulting Ltd | Information & communication | 2011 |
| Greycaine Furniture Ltd | Manufacturing | 2017 |
| Greycaine Limited | Real estate | 2015 |
| Greystone Properties Hampton Court Limited | Real estate | 2021 |
| Greystone Roofing Ltd | Construction | 2026 |
| Grid Apex Solutions Ltd | Professional & scientific | 2026 |
| Gridlock Media Limited | Information & communication | 2010 |
| Grieve Freely Ltd | Health & social care | 2022 |
| Grif Corporation LLP | | 2005 |
| Griffin Transport UK Limited | Transport & logistics | 2021 |
| Griffon Properties Limited | Real estate | 2002 |
| Griggs Electrical Services (GES) Limited | Construction | 2015 |
| Grigore Bizga Ltd | Construction | 2024 |
| Griguta Construct Ltd | Construction | 2019 |
| Grill Express Ltd | Hospitality | 2019 |
| Grillheath Limited | Real estate | 1973 |
| GRM & Developers Limited | Construction | 2024 |
| GRM Energy Ltd | Construction | 2022 |
| GRM Infra Ltd | Manufacturing | 2026 |
| GRM Nexus Ltd | Energy | 2026 |
| GRM Power House Ltd | Energy | 2025 |
| GRM Power Ltd | Energy | 2025 |
| GRM Sustainable Systems Ltd | Manufacturing | 2026 |
| GRM Transport Limited | Transport & logistics | 2013 |
| GRO System LP | | 2017 |
| Grobal Healthcare Ltd | Administrative & support | 2025 |
| Groove Music (Watford) Ltd | Education | 2024 |
| Gross Air Ltd | Administrative & support | 2020 |
| Grosvenor Court (ST Albans) Limited | Households | 1993 |
| Groszek Ltd | Wholesale & retail | 2009 |
| Ground Force Group Ltd | Administrative & support | 2022 |
| Ground Force Services Ltd | Construction | 2016 |
| Ground Rent Estates 3 Limited | Real estate | 2006 |
| Ground Rent Estates 6 Limited | Real estate | 2004 |
| Grounded Retreats Limited | Real estate | 2020 |
| Groundworks Project Ltd | Arts & recreation | 2026 |
| Group for the Rootless of Watford (G.R.O.W.) | Health & social care | 1986 |
| Group W Ltd | Professional & scientific | 2025 |
| Grove Apartments (Stratford) Management Company Limited | Households | 2009 |
| Grove Court RTM Company Limited | Households | 2016 |
| Grove Green Estates Ltd | Real estate | 2018 |
| Grove Park House Limited | Households | 2001 |
| Grovewood Ltd | Extraterritorial | 2014 |
| Grow Plus Limited | Agriculture & fishing | 2016 |
| Growing Together Building Project Ltd | Construction | 2026 |
| Growmore Travel Ltd | Administrative & support | 2020 |