| Key Systems UK Ltd | Administrative & support | 2007 |
| Key Traceability Ltd. | Professional & scientific | 2015 |
| Keydell Commercial Interiors Limited | Construction | 2009 |
| Keynest Property Ltd | Real estate | 2025 |
| Keyto Contracting Limited | Administrative & support | 2023 |
| Keyto Group Holdings Limited | Financial services | 2025 |
| Keyto Group Limited | Administrative & support | 2023 |
| Keyto Outsourcing Limited | Administrative & support | 2022 |
| Keyto Project Services Limited | Administrative & support | 2022 |
| KF Autos Limited | Wholesale & retail | 2022 |
| Kfix Flat Roofing Limited | Construction | 2016 |
| KGJ Property Ltd | Construction | 2026 |
| KGP Contracts Ltd | Administrative & support | 2014 |
| KGS Developments Limited | Real estate | 2024 |
| KGS Mechanical Limited | Construction | 2014 |
| KH Private Ltd | Wholesale & retail | 2025 |
| KH Tools & SON Limited | Wholesale & retail | 2025 |
| Khalemmric Ltd | Financial services | 2017 |
| Khalsa Properties Limited | Real estate | 1997 |
| Khan Industry Ltd | Professional & scientific | 2024 |
| Kicks FC Ltd | Arts & recreation | 2025 |
| Kidbrook Estates Limited | Real estate | 2023 |
| Kiddiname Limited | Extraterritorial | 2014 |
| Kidz World Events Ltd | Arts & recreation | 2022 |
| Kilburn Primary Care Co-Op Limited | Health & social care | 2009 |
| Killeen Plant Limited | Professional & scientific | 1990 |
| Kiltec Engineering Limited | Administrative & support | 2013 |
| Kinan Limited | Real estate | 2022 |
| Kindle House Events Ltd | Hospitality | 2026 |
| King James Gate Moorings Limited | Arts & recreation | 2005 |
| King James' Gate (Portsmouth) Residents Association Limited | Households | 1987 |
| King's Group Academies | Education | 2014 |
| Kingdom Grill Ltd | Hospitality | 2025 |
| Kingdom of Eden Ltd | Professional & scientific | 2026 |
| Kingfisher Court RTM Company Ltd | Administrative & support | 2009 |
| Kingfisher Lettings Ltd | Real estate | 2011 |
| Kingfisher Property Group Ltd | Administrative & support | 2016 |
| Kingfisher Property Services Ltd | Administrative & support | 2016 |
| Kings Building Services Ltd | Construction | 2023 |
| Kings Marine Limited | Other services | 1997 |
| Kings Mews (Southsea) Management Company Limited | Hospitality | 2000 |
| Kings Quay Maintenance Company Limited | Real estate | 1965 |
| Kingsbere Homes Ltd | Real estate | 2024 |
| Kingscote Villas Ltd | Households | 2010 |
| Kingsley Garage Limited | Wholesale & retail | 2024 |
| Kingsmead Properties Limited | Real estate | 2016 |
| Kingstion Mini Market Ltd | Wholesale & retail | 2026 |
| Kingston Cleaners Limited | Other services | 2002 |
| Kingston Crescent Management Ltd | Households | 2019 |
| Kingston House (Portsmouth) RTM Company Limited | Households | 2019 |
| Kinto UK Limited | Wholesale & retail | 1965 |
| Kiota Recruitment Ltd | Administrative & support | 2020 |
| KIP23 Ltd | Hospitality | 2022 |
| Kippson Media Limited | Wholesale & retail | 2011 |
| Kiranrehmanltd Limited | Wholesale & retail | 2025 |
| Kirby Decor Ltd | Construction | 2019 |
| Kirin Consulting Limited | Information & communication | 2013 |
| Kisco (UK) Limited | Administrative & support | 2009 |
| Kitchen Kraft Ltd | Hospitality | 2023 |
| Kitsune Technology Limited | Information & communication | 2022 |
| Kiyak Ltd | Real estate | 2026 |
| KJ Lifting Ltd | Construction | 2018 |
| KJ Payroll & Admin Services Ltd | Professional & scientific | 2016 |
| KJ Roofing Services Ltd | Construction | 2012 |
| KJG Motors Limited | Wholesale & retail | 2026 |
| KJM Media Ltd | Professional & scientific | 2019 |
| KJR Catering Ltd | Hospitality | 2024 |
| KJR Properties Limited | Professional & scientific | 1997 |
| KK Ductwork Ltd | Construction | 2017 |
| KKM (Hampshire) Limited | Administrative & support | 2015 |
| Kksd Ltd | Real estate | 2026 |
| KL Fibre Limited | Manufacturing | 2024 |
| Kleene Solutions Limited | Administrative & support | 2025 |
| Kliment Paskalev Limited | Information & communication | 2023 |
| KLM Plumbing, Heating & Electrical Ltd | Construction | 2021 |
| KLW Construction Ltd | Construction | 2020 |
| KM Plumbing & Heating Ltd | Construction | 2016 |
| KM Property Empire Limited | Real estate | 2024 |
| KM Solent Limited | Hospitality | 2014 |
| KM Tradez Ltd | Wholesale & retail | 2024 |
| Kmukoko Limited | Health & social care | 2017 |
| KNE Consulting Limited | Professional & scientific | 2017 |
| Knebworth Festival Wear Ltd | Wholesale & retail | 2024 |
| Knight & MAY Joinery Limited | Manufacturing | 2009 |
| Knight & Wilson Limited | Wholesale & retail | 2014 |
| Knight & Wilson Trading Limited | Wholesale & retail | 2014 |
| Knight Landlord Services Limited | Administrative & support | 2019 |
| Knight Maritime Ltd | Professional & scientific | 2024 |
| Knights Department Store Limited | Wholesale & retail | 2019 |
| Knightwood Solutions Ltd | Construction | 2017 |
| Knightwood Southern Limited | Construction | 2026 |
| Knowbridge Limited | Education | 2024 |
| Known for Group Limited | Professional & scientific | 2022 |
| Knownow Information Ltd | Information & communication | 2013 |
| KNS Global Ltd | Real estate | 2026 |
| Kodasoft Limited | Information & communication | 2023 |
| Kodawaste Limited | Information & communication | 2025 |
| Kogresta Ltd | Construction | 2017 |
| Kokoro Portsmouth Ltd | Hospitality | 2022 |
| Kongday Ltd | Professional & scientific | 2022 |