| A Robbins Engineering Services Ltd | Professional & scientific | 2006 |
| A V Consultancy Group Ltd | Information & communication | 2021 |
| A Wild Life CIC | Professional & scientific | 2025 |
| A&G Technical Writing Services Limited | Professional & scientific | 2026 |
| A&I Leisure Ltd | Real estate | 2019 |
| A&M Properties (South) Ltd | Real estate | 2019 |
| A&P Entertainment Ltd | Arts & recreation | 2021 |
| A&R Cars Sussex Limited | Transport & logistics | 2021 |
| A&Y Electrical Limited | Construction | 2010 |
| A-Stute Flooring Co. Ltd | Construction | 2025 |
| A. Barrell Limited | Construction | 2005 |
| A. Purkiss Building & Decorating Contractors Limited | Construction | 1998 |
| A.C.T. Consultant Services Limited | Professional & scientific | 2019 |
| A.J. Systems (UK) Limited | Administrative & support | 1991 |
| A.Johni Life Science Consulting Ltd | Professional & scientific | 2023 |
| A.R. Moore Ltd | Construction | 2007 |
| A1 Security Protection Limited | Administrative & support | 2023 |
| A2Z Lifestyle Solutions Ltd | Wholesale & retail | 2024 |
| A2Z Private Limited | Financial services | 2019 |
| A320LPC Ltd | Transport & logistics | 2011 |
| A320READY Ltd | Education | 2026 |
| AAA Care Solutions Ltd | Health & social care | 2017 |
| AAA Transport (Horsham) Ltd | Transport & logistics | 2020 |
| AAP Properties (Southern) Limited | Real estate | 1996 |
| Aaryan Properties Horsham Limited | Real estate | 2024 |
| Aball Construction Limited | Construction | 2001 |
| Abba Amma Film Limited | Information & communication | 2023 |
| Abbectim Ltd | Information & communication | 2012 |
| Abbey Care Maintenance and Renovations Ltd | Administrative & support | 2016 |
| Abbeyoaks Stud Ltd | Other services | 2026 |
| ABC Classics Limited | Wholesale & retail | 2021 |
| ABC GAS Plumbing & Heating Limited | Construction | 2017 |
| ABC Sound Limited | Professional & scientific | 2011 |
| Abchurch Communications Ltd | Administrative & support | 2004 |
| ABL Consultants Ltd | Professional & scientific | 2018 |
| ABM Building Services Limited | Construction | 2002 |
| Abmbuild Limited | Construction | 2012 |
| Abnhholdings Limited | Administrative & support | 2023 |
| Abode Finance Ltd | Financial services | 2018 |
| Abode Therapy Ltd | Professional & scientific | 2020 |
| About Mortgages Ltd | Financial services | 2018 |
| About Soban Ltd | Wholesale & retail | 2025 |
| About Town Motorcycle & Scooter Hire Limited | Wholesale & retail | 2000 |
| ACA Publishing Limited | Information & communication | 2007 |
| ACB Surveyors Ltd | Professional & scientific | 2023 |
| ACC Leisure Maintenance Limited | Construction | 2013 |
| Access Knowledge & Training Ltd | Construction | 2011 |
| Accio BI Limited | Information & communication | 2016 |
| Ace Breakers Limited | Construction | 2019 |
| Ace Electrical Services Ltd | Construction | 2018 |
| Ace Spray Limited | Construction | 2010 |
| Ace-Doughnuts Ltd | Manufacturing | 2021 |
| Acefern Limited | Health & social care | 2019 |
| Acer Enterprises Ltd | Professional & scientific | 2003 |
| Acer Property Group Limited | Real estate | 2026 |
| ACG Europe Limited | Wholesale & retail | 2003 |
| ACG Global Services Limited | Administrative & support | 2024 |
| ACI Biotech (Holdings) Limited | Professional & scientific | 2024 |
| ACK Solutions Ltd | Professional & scientific | 1999 |
| Acme Racing Limited | Information & communication | 2019 |
| Acme UC Limited | Information & communication | 2019 |
| Acorn Contractors Limited | Construction | 1984 |
| Acorn Fire Protection Ltd | Public administration | 2026 |
| Acorn Surveyors Limited | Professional & scientific | 2006 |
| Acorn Therapy Clinics Ltd | Health & social care | 2008 |
| ACP Music Ltd | Administrative & support | 2004 |
| Acre Mortgages Limited | Financial services | 2024 |
| Acro Aviation Services Limited | Professional & scientific | 2025 |
| Active Facilitation Ltd | Education | 2026 |
| Acuity Group Ltd | Professional & scientific | 2007 |
| Acuity Invest Limited | Real estate | 2020 |
| AD Autotechnik Limited | Wholesale & retail | 2008 |
| Adam Wishart Limited | Information & communication | 2000 |
| Adam Wylie Limited | Wholesale & retail | 2002 |
| Adamson MCS Limited | Professional & scientific | 2017 |
| Adamson MCS Properties Ltd | Real estate | 2024 |
| Adasoos Ltd | Construction | 2024 |
| Adcredidi Ltd | Real estate | 2026 |
| Addblend Limited | Financial services | 1999 |
| Address Estate Agents Limited | Real estate | 2007 |
| Address Limited | Professional & scientific | 2014 |
| Addspeed Performance Cars Limited | Wholesale & retail | 2002 |
| ADE Keeley Ltd | Hospitality | 2020 |
| Adelphia Solutions Limited | Professional & scientific | 2020 |
| Adeo Global Consulting Ltd | Professional & scientific | 2005 |
| Adeo Property Developments (Compton's Lane) Ltd | Administrative & support | 2016 |
| Adeo Property Management Limited | Administrative & support | 2009 |
| Adesigner Limited | Administrative & support | 2016 |
| Adjudication Limited | Professional & scientific | 2003 |
| ADM Training Ltd | Professional & scientific | 2011 |
| Adnitor Limited | Information & communication | 2019 |
| Adolescent Dogs Ltd | Professional & scientific | 2014 |
| Adrian Mobile Locksmith Limited | Manufacturing | 2008 |
| ADS Gardens (Sussex) Ltd. | Administrative & support | 2017 |
| Advance Chimney Cameras Ltd | Manufacturing | 2024 |
| Advance H2O Solutions Limited | Transport & logistics | 2013 |
| Advance Property Services Limited | Hospitality | 2002 |
| Advanced Cleaning Equipment Services Limited | Wholesale & retail | 2000 |
| Advanced Electronic Designs Ltd | Manufacturing | 1998 |
| Advanced Partitions Ltd | Construction | 2022 |