| 85 Sylvan Avenue Freehold Company Limited | Extraterritorial | 2012 |
| 88 Key Creations Ltd | Information & communication | 2024 |
| 93 High Street Limited | Real estate | 2026 |
| 99 High Street Ltd | Hospitality | 2022 |
| A & D Electrical Services (Herts) Limited | Construction | 2017 |
| A & I Trading Limited | Information & communication | 2001 |
| A & R Renewable's Ltd | Water & waste | 2025 |
| A B Properties Investments Limited | Real estate | 2018 |
| A C Lime Plastering & Rendering Ltd | Construction | 2026 |
| A C S (2000) Limited | Construction | 2000 |
| A Class Air-Conditioning Systems Limited | Construction | 2020 |
| A Florea Ltd | Construction | 2018 |
| A G F Fire Protection Ltd | Administrative & support | 2003 |
| A Helping Hoof - Learning & Support Ltd | Education | 2025 |
| A Helping Hoof Ltd | Education | 2022 |
| A J Mccarthy Carpentry & Joinery Ltd | Construction | 2014 |
| A List and Sons Bars Ltd | Hospitality | 2024 |
| A List and Sons Foods Ltd | Hospitality | 2025 |
| A M S Doors Limited | Manufacturing | 2011 |
| A Mcclement Imaging Ltd | Health & social care | 2025 |
| A Meta Limited | Construction | 2026 |
| A N F Construction Limited | Construction | 2015 |
| A P Solutions 2022 Ltd | Administrative & support | 2022 |
| A Plus Brickwork Ltd | Construction | 2013 |
| A Plus Capital Partners Ltd | Financial services | 2025 |
| A Plus Group Holdings Ltd | Financial services | 2025 |
| A Qose Construction Ltd | Construction | 2023 |
| A R Initiative Limited | Information & communication | 2010 |
| A Running Commentary Productions Ltd | Information & communication | 2025 |
| A S Coonar Limited | Professional & scientific | 2011 |
| A Sama Healthcare Ltd | Health & social care | 2019 |
| A Spicer Utilities Limited | Water & waste | 2025 |
| A U Medical Services Limited | Health & social care | 2012 |
| A Woman Empowered (AWE) Limited | Professional & scientific | 2013 |
| A&A Construction and Maintenance Ltd | Construction | 2019 |
| A&A Development Properties Ltd | Real estate | 2025 |
| A&J Lowe Holdings Ltd | Financial services | 2025 |
| A&J Management Cosultants Ltd | Other services | 2019 |
| A&L Tiger Limited | Hospitality | 2024 |
| A&M Residential Properties Ltd | Real estate | 2025 |
| A&N Independence Ltd | Information & communication | 2025 |
| A&O Resources Limited | Health & social care | 2019 |
| A&R Films Limited | Information & communication | 2018 |
| A-Wan Development Ltd | Construction | 2026 |
| A-Z Basketball Limited | Education | 2019 |
| A. Blacow Films Limited | Other services | 2021 |
| A. Lastauskas Limited | Health & social care | 2013 |
| A.C.&Co Developments Ltd | Hospitality | 2023 |
| A.D. Practice Limited | Professional & scientific | 2002 |
| A.G.S. Maintenance & Services Limited | Wholesale & retail | 2026 |
| A.Godshaw Limited | Wholesale & retail | 1958 |
| A.R.K. Lasting Powers & Wills Ltd | Other services | 2018 |
| A.S.M Windows Limited | Construction | 2019 |
| A.T.James Plumbing & Heating Limited | Construction | 2012 |
| A1 BN UK Limited | Wholesale & retail | 2003 |
| A1 Carpet & Flooring Limited | Wholesale & retail | 2007 |
| A1 Couriers Limited | Transport & logistics | 2018 |
| A1TECHFLOW Ltd | Information & communication | 2026 |
| A2B Construction Services Ltd | Construction | 2023 |
| AA Cabs (Stevenage) Limited | Transport & logistics | 2025 |
| AA Foodies Ltd | Hospitality | 2019 |
| AA Heritage Homes Ltd | Real estate | 2025 |
| AA Venture Properties Ltd | Households | 2023 |
| AAA Building & Property Services Ltd | Construction | 2025 |
| Aabc Aggregates Ltd | Mining & quarrying | 2015 |
| Aabc Bagging Ltd. | Wholesale & retail | 2001 |
| Aabc Bidco Limited | Financial services | 2023 |
| Aabc Group Ltd | Professional & scientific | 2014 |
| Aabc Logistics Ltd | Administrative & support | 2015 |
| Aabc Materials Ltd | Mining & quarrying | 1991 |
| Aabc Recycling Ltd | Mining & quarrying | 2017 |
| Aabc Topco Limited | Financial services | 2021 |
| Aabdp Ltd | Health & social care | 2025 |
| Aara Medical Limited | Health & social care | 2023 |
| Aaron Composite Services Ltd | Manufacturing | 2022 |
| AB BIO Couriers Limited | Transport & logistics | 2024 |
| AB Business Solutions Limited | Administrative & support | 2011 |
| ABA Property Hub Ltd | Real estate | 2025 |
| Abacus Electrical Herts Limited | Construction | 2009 |
| Abah Group Limited | Other services | 2023 |
| Abalo Consultancy Limited | Financial services | 2017 |
| Abaye Management Limited | Professional & scientific | 2014 |
| Abba Adonai Healthcare Services Ltd | Health & social care | 2020 |
| Abbots Barn Ltd | Health & social care | 2026 |
| Abbots Green (Arlesey) Management Company Limited | Households | 2006 |
| Abbott Taxi Limited | Transport & logistics | 2024 |
| Abbyfreddy Limited | Administrative & support | 2025 |
| ABC Minor Ltd | Wholesale & retail | 2023 |
| ABC Taxis (Stevenage) Limited | Transport & logistics | 2008 |
| Abcd Education Services Ltd | Education | 2026 |
| Abdul-Hamid Healthcare Limited | Health & social care | 2024 |
| Abery Motor Centre Limited | Wholesale & retail | 2003 |
| Abex and Associates Ltd | Health & social care | 2022 |
| ABH Automotive Ltd | Wholesale & retail | 2022 |
| Ability Greens Ltd | Wholesale & retail | 2024 |
| ABK Property Ltd | Real estate | 2021 |
| Able Groundworks & Construction Limited | Construction | 2018 |
| Above & Beyond Meats Ltd | Wholesale & retail | 2020 |
| Abraham Plant Limited | Other services | 2020 |
| Abraham Scaffolding Limited | Construction | 2015 |