| Fitzgerald Welding Solutions Limited | Professional & scientific | 2013 |
| Flatraterecruitment Group Limited | Administrative & support | 2016 |
| Flying Leisure Limited | Hospitality | 2011 |
| Flying Trade Group Limited | Professional & scientific | 1989 |
| Flying Trade Limited | Wholesale & retail | 1988 |
| Food for Thought Community Projects CIC | Hospitality | 2024 |
| FOX Online Solutions Ltd | Information & communication | 2012 |
| Freelance Brickwork Ltd | Construction | 2018 |
| Freeport East Limited | Public administration | 2022 |
| Freestyle Performing Arts CIC | Health & social care | 2025 |
| Fresh Drives Limited | Administrative & support | 2020 |
| Frobisher Catering Ltd | Hospitality | 2024 |
| Funnelwick Limb CIC | Administrative & support | 2019 |
| Fwtv Ltd | Information & communication | 2025 |
| G T Exhibitions Limited | Transport & logistics | 2000 |
| G&S Properties Limited | Construction | 2018 |
| GB Customs Clearance Limited | Transport & logistics | 2020 |
| GB Logistics Group Ltd | Financial services | 2023 |
| GB Warehouse & Transport Limited | Transport & logistics | 2023 |
| GEE GRP Fibreglassing Ltd | Manufacturing | 2012 |
| GEL United Limited | Manufacturing | 2025 |
| George Thompson (Great Oakley) Limited | Agriculture & fishing | 1948 |
| GEP Installation and Maintenance Services Ltd | Construction | 2022 |
| Gilead Films Ltd | Information & communication | 2024 |
| Gilead Lifts Ltd | Construction | 2018 |
| Glenbrook Constructions Limited | Professional & scientific | 2013 |
| Glynis Peters Limited | Information & communication | 2019 |
| GMC Haulage Ltd | Transport & logistics | 2023 |
| Good's Bespoke Interiors Ltd | Construction | 2026 |
| GPR Garden & Property Renovations Limited | Construction | 2024 |
| Greatborn Solutions Limited | Wholesale & retail | 2022 |
| H Hambling Limited | Construction | 2017 |
| H&B Civils Ltd | Construction | 2025 |
| H&V Property Limited | Real estate | 2025 |
| H.S. & K.M. Nurkowski & Co Limited | Construction | 1987 |
| H.T. Packing and Distribution Limited | Transport & logistics | 2000 |
| Hair Bythe Station Limited | Other services | 2022 |
| Haltermann Carless UK Limited | Manufacturing | 1947 |
| Hamford View Limited | Hospitality | 2017 |
| Hamilton RPF Ltd | Financial services | 2020 |
| Hanslip Ward & Co. Ltd | Professional & scientific | 2003 |
| Happy Sales Limited | Wholesale & retail | 2024 |
| Harwich & Dovercourt Bay Carpets Ltd | Wholesale & retail | 2024 |
| Harwich & Dovercourt Properties Limited | Hospitality | 2023 |
| Harwich and District Indoor Bowls Centre Trustee Limited | Arts & recreation | 1999 |
| Harwich Cancer Support Group CIC | Health & social care | 2025 |
| Harwich Chicken Ltd | Hospitality | 2023 |
| Harwich Commercials Ltd | Wholesale & retail | 2025 |
| Harwich Community Clearances Ltd | Wholesale & retail | 2025 |
| Harwich Connexions Community Catering Ltd | Hospitality | 2021 |
| Harwich Connexions Community Trust | Real estate | 2006 |
| Harwich Connexions Noah's Nursery Ltd | Education | 2008 |
| Harwich Connexions Transport Co-Operative Limited | Transport & logistics | 2003 |
| Harwich Connexions Windmill Nursery Limited | Health & social care | 2024 |
| Harwich Cricket Club Ltd | Arts & recreation | 2021 |
| Harwich Cultural & Community Projects Ltd | Education | 2009 |
| Harwich Dock Company Limited | Transport & logistics | 1963 |
| Harwich Food Limited | Hospitality | 2025 |
| Harwich Glass and Window Co Ltd | Construction | 1991 |
| Harwich Hand Car Wash Ltd | Administrative & support | 2016 |
| Harwich Harbour Ltd | Hospitality | 2025 |
| Harwich Masonic Hall Company Limited | Other services | 1988 |
| Harwich Mobility Services Ltd | Wholesale & retail | 2023 |
| Harwich Museum | Arts & recreation | 2020 |
| Harwich Nails Ltd | Other services | 2024 |
| Harwich Property Company Limited | Administrative & support | 2010 |
| Harwich Quay Fireworks Ltd | Arts & recreation | 2025 |
| Harwich Supplies Limited | Wholesale & retail | 1992 |
| Harwich Taxis Limited | Extraterritorial | 2026 |
| Harwich Time and Tide Bell Community Interest Company | Arts & recreation | 2023 |
| Harwich Town Locksmiths Limited | Manufacturing | 2018 |
| Harwichhall Limited | Real estate | 2022 |
| Haven Dredging Ltd | Construction | 2022 |
| Haven Pilots LLP | | 2013 |
| Hawkins & Clark Brickwork Contractors Ltd | Construction | 2017 |
| Hayes & Hearth Holdings Limited | Real estate | 2025 |
| HC Landscapes and Groundworks Ltd | Administrative & support | 2025 |
| Healey Plant Sales Ltd | Wholesale & retail | 2025 |
| Heinloth UK Limited | Transport & logistics | 2018 |
| Heliclean East Anglia Limited | Administrative & support | 2009 |
| Henson Installations Ltd | Construction | 2023 |
| HGD Limited | Professional & scientific | 2024 |
| HGW Homes Ltd | Real estate | 2025 |
| High Oaks Management Company Limited | Households | 2000 |
| Highwood International Limited | Hospitality | 2016 |
| Hill Road Management Company Limited | Households | 2008 |
| Hilltop Rise Residents Limited | Hospitality | 2015 |
| HJ Blair Properties Limited | Real estate | 2019 |
| HMG Vehicle Services Ltd | Wholesale & retail | 1996 |
| HMS Industrial Roofing Limited | Construction | 2017 |
| Homcraft Ltd | Wholesale & retail | 2024 |
| Home of Biab Ltd | Other services | 2025 |
| Home-Baked by the Quay Ltd | Hospitality | 2024 |
| Home-Start Harwich | Health & social care | 2006 |
| Honeypot Holistic Therapies C.I.C. | Health & social care | 2022 |
| Hoobal Ltd | Information & communication | 2024 |
| Hortland Construction Limited | Professional & scientific | 2013 |
| HPE (UK) Limited | Manufacturing | 2000 |
| HRL Plumbing & Heating Services Ltd | Construction | 2017 |
| HS Garden Maintenance and Tree Services Ltd | Administrative & support | 2025 |