| ABC Investments (Hitchin) Limited | Financial services | 2022 |
| Abdul Nadeem Ltd | Wholesale & retail | 2026 |
| Abdulsamad AL Qurashi Limited | Wholesale & retail | 2016 |
| ABL Partners Ltd | Financial services | 2020 |
| Abode Green Ltd | Real estate | 2021 |
| Abode Land and Property Ltd | Construction | 2025 |
| Abodely Ltd | Real estate | 2023 |
| Above and Beneath Ltd | Information & communication | 2022 |
| Abrams Archaeology Limited | Professional & scientific | 2020 |
| Absent Friends Pet Crematorium Limited | Other services | 2014 |
| Absolute Creative Ltd | Professional & scientific | 2017 |
| AC Townsend Holdings Limited | Financial services | 2026 |
| Academy NOW Ltd | Other services | 2023 |
| ACB Resource Ltd | Administrative & support | 2010 |
| Acca Chicken Limited | Hospitality | 2026 |
| Acca FG Limited | Other services | 2025 |
| Acca Foods Limited | Hospitality | 2023 |
| Acca Group Limited | Financial services | 2020 |
| Acca House Limited | Other services | 2024 |
| Acca Land Limited | Real estate | 2008 |
| Acca Limited | Hospitality | 2002 |
| Acca Office Limited | Real estate | 2018 |
| Accelerating Commercial Excellence LLP | | 2023 |
| Accent Park Ltd | Real estate | 2020 |
| Accent Security Limited | Administrative & support | 2009 |
| Accentura Ltd | Wholesale & retail | 2007 |
| Accountants by the Hour LLP | | 2017 |
| Accra Taps and Valves Ltd | Manufacturing | 2022 |
| Ace Hose and Hydraulics Ltd | Administrative & support | 2012 |
| Ace of Herts Event Management Ltd | Administrative & support | 2019 |
| Ace of Herts Ltd | Manufacturing | 2010 |
| ACI Directors Limited | Administrative & support | 2014 |
| ACM Business Services Limited | Administrative & support | 2017 |
| ACP Baits Ltd | Wholesale & retail | 2021 |
| Acre & ROW Ltd | Wholesale & retail | 2020 |
| Actcap Limited | Financial services | 2020 |
| Activ Investments Limited | Real estate | 2016 |
| Activate Psychology Ltd | Health & social care | 2024 |
| Active Fintech Limited | Real estate | 2012 |
| Acumen Insights Ltd | Information & communication | 2003 |
| Acumen Research Limited | Information & communication | 2022 |
| Acura Foods Ltd | Wholesale & retail | 2002 |
| Acurizon Consulting Ltd | Information & communication | 2025 |
| AD Electrical Contractors Limited | Construction | 2006 |
| Adam Bradford Limited | Information & communication | 2006 |
| Adam Farm Fresh Limited | Wholesale & retail | 2020 |
| Adapt EMS Ltd | Manufacturing | 1985 |
| Adaptogenics Limited | Financial services | 2021 |
| Addaptive Group Holdings Limited | Financial services | 2020 |
| Addaptive Group Limited | Professional & scientific | 2020 |
| Addison London Limited | Real estate | 1988 |
| Addison Mason Limited | Financial services | 2022 |
| ADE Hopkins Limited | Professional & scientific | 2017 |
| Adelaide Construction Ltd | Construction | 2016 |
| Adelphi Funding Limited | Administrative & support | 2000 |
| Ademe Limited | Real estate | 2014 |
| Adibnia Ltd | Education | 2025 |
| Adimpact Ltd | Health & social care | 2023 |
| Adpretio Ltd | Information & communication | 2013 |
| ADS Joinery Limited | Manufacturing | 2012 |
| Adult Panto Limited | Arts & recreation | 2017 |
| Adulting Cards Ltd | Wholesale & retail | 2018 |
| Advance Productivity Ltd | Administrative & support | 2020 |
| Advance Sunny Spain Limited | Extraterritorial | 2004 |
| Advance View Consulting Ltd | Professional & scientific | 2023 |
| Adventure Drone Biker Tours Ltd | Administrative & support | 2024 |
| Adventure Play Limited | Arts & recreation | 2009 |
| Adversa Recruitment Limited | Administrative & support | 2017 |
| Advias Ltd | Financial services | 2021 |
| Advize Ltd | Professional & scientific | 2025 |
| Aecsys Technologies Ltd | Information & communication | 2005 |
| Aeoliki Marine Limited | Information & communication | 2000 |
| Aerien Limited | Transport & logistics | 2021 |
| Aerogriduk Ltd | Transport & logistics | 2024 |
| Aerospeed Ltd | Transport & logistics | 1999 |
| Aessis Consulting Ltd | Information & communication | 2021 |
| Aessis Ltd | Information & communication | 2007 |
| Aesthetics Bar Herts Ltd | Other services | 2020 |
| Aevitas Properties Limited | Real estate | 2020 |
| Affective Minds Ltd | Professional & scientific | 2021 |
| Affinity 3 Ltd | Professional & scientific | 2022 |
| Afif Consulting Ltd | Information & communication | 2026 |
| After My Limited | Professional & scientific | 2024 |
| AG Dental Prosthetics Limited | Health & social care | 2023 |
| AG Talent Ltd | Administrative & support | 2024 |
| Agecare Support Limited | Health & social care | 2021 |
| Agent Hitchin Limited | Real estate | 2008 |
| Aggmore 2 Limited | Real estate | 2000 |
| Aggmore 6 Limited | Real estate | 2006 |
| Aggmore Commercial Properties Limited | Real estate | 1998 |
| Aggmore Limited | Construction | 2005 |
| Aggmore Properties Limited | Real estate | 1999 |
| Aggmore Ventures CE LLP | | 2006 |
| Agiaerospace Ltd | Wholesale & retail | 2024 |
| AGILITY3 Limited | Information & communication | 2012 |
| Agos Healthcare Limited | Professional & scientific | 2016 |
| Agos Pharma Limited | Professional & scientific | 2019 |
| Agosit Limited | Information & communication | 2019 |
| AGR Space Ltd | Professional & scientific | 2022 |
| Agrisect Ltd | Manufacturing | 2020 |