| Activate Products Limited | Wholesale & retail | 2013 |
| Active 4 Sport CIC | Education | 2025 |
| Active Approach Ltd | Health & social care | 2026 |
| Active Body Care Limited | Health & social care | 2007 |
| Active Companions Ltd | Health & social care | 2023 |
| Active Homes Ltd | Construction | 2026 |
| Active Removals Ltd | Transport & logistics | 2022 |
| ACTIVE8 Aviation Ltd | Professional & scientific | 2017 |
| Activepowr UK Ltd | Wholesale & retail | 2015 |
| Activity Leisure Group Ltd | Arts & recreation | 2018 |
| Actors Studio Ltd | Information & communication | 2023 |
| Actual Realty Ltd | Real estate | 2023 |
| Actual Recycling Ltd | Wholesale & retail | 2023 |
| Actually Delicious Ltd | Information & communication | 2024 |
| Acute Notions Ltd | Information & communication | 2022 |
| AD Angels Limited | Arts & recreation | 2011 |
| AD Astra Construction Ltd | Construction | 2021 |
| AD Astra Financial Services Ltd | Financial services | 2021 |
| AD Astra Learning Ltd | Education | 2015 |
| AD Astra Property Solutions Ltd | Construction | 2020 |
| AD Astra Tuition Ltd | Education | 2013 |
| AD Astra Z Ltd | Professional & scientific | 2021 |
| AD Luxe Ltd | Wholesale & retail | 2026 |
| AD Security Services Ltd | Administrative & support | 2022 |
| Adagiovr Ltd | Information & communication | 2021 |
| Adak Consultancy Ltd | Information & communication | 2016 |
| Adam Abdullah Ltd | Wholesale & retail | 2025 |
| Adam Accountancy Limited | Professional & scientific | 2016 |
| Adam Accountants Limited | Professional & scientific | 2016 |
| Adam AJ Blinds Ltd | Construction | 2021 |
| Adam and Eve's Children's Educational and Welfare Ltd | Education | 2025 |
| Adam Plumbing, Heating & Construction Ltd | Construction | 2025 |
| Adam Steel Fittings Limited | Construction | 2015 |
| Adam UK Security Limited | Administrative & support | 2018 |
| Adam's Repairs and Supply Ltd | Manufacturing | 2025 |
| Adan Technology Ltd | Information & communication | 2022 |
| Adan Trading Ltd | Wholesale & retail | 2025 |
| Adanet Security Solutions Ltd | Construction | 2025 |
| Adapt Avenue Ltd | Wholesale & retail | 2016 |
| Adapt Construction Group Ltd | Construction | 2022 |
| Adapt OR DIE Ltd | Information & communication | 2025 |
| Adapt Systems Limited | Information & communication | 2012 |
| Adastra a Ltd | Education | 2025 |
| Adasu Limited | Hospitality | 2013 |
| ADC Roofing and Cladding Ltd | Construction | 2024 |
| Adcrate Ltd | Professional & scientific | 2022 |
| ADD Zest Limited | Administrative & support | 1997 |
| Addenbrooke Investments Ltd | Real estate | 2026 |
| Addingrove Ltd | Information & communication | 2023 |
| Addison Alfie Limited | Real estate | 2020 |
| Additions Plus Ltd | Professional & scientific | 2017 |
| Adds Health Limited | Health & social care | 2022 |
| Addsoft Solutions Limited | Information & communication | 2016 |
| Adealon Limited | Administrative & support | 2007 |
| Adels Alternative Solutions Ltd | Wholesale & retail | 2025 |
| Adept AI Solutions Ltd | Information & communication | 2024 |
| Adfanco Ltd | Wholesale & retail | 2024 |
| Adforceglobal Ltd | Professional & scientific | 2025 |
| Adhd in Business Ltd | Professional & scientific | 2022 |
| Adhiti Limited | Administrative & support | 2011 |
| ADI & Co Accountants Limited | Professional & scientific | 2015 |
| Adiash Ltd | Wholesale & retail | 2025 |
| Adiha Limited | Hospitality | 2025 |
| Adime Limited | Professional & scientific | 2022 |
| Adinde and SON Care Provider Ltd | Health & social care | 2016 |
| Aditi Homes Ltd | Hospitality | 2022 |
| Adivta Limited | Health & social care | 2023 |
| ADL (Southern) Ltd | Construction | 2019 |
| Adlam Solutions Ltd | Wholesale & retail | 2021 |
| Adlib Digital Limited | Information & communication | 2017 |
| ADM Security Services Ltd | Administrative & support | 2024 |
| Admal Transport Ltd | Transport & logistics | 2022 |
| Admire Care Limited | Health & social care | 2023 |
| Admodum Ltd | Information & communication | 2017 |
| Admore Construction Ltd | Construction | 2026 |
| ADO Auto Limited | Wholesale & retail | 2023 |
| Adolce Ltd | Wholesale & retail | 2025 |
| Adom Soul of Africa Ltd | Hospitality | 2025 |
| Adomnhyira Co. Limited | Health & social care | 2019 |
| Adono Services Ltd | Transport & logistics | 2019 |
| Adorned by Simi Ltd | Wholesale & retail | 2026 |
| ADR Aero Ltd | Wholesale & retail | 2026 |
| ADR Engineering Solutions Ltd | Wholesale & retail | 2015 |
| Adrian Electrical Services Limited | Construction | 2025 |
| Adrian Morris & Co. Limited | Construction | 2021 |
| Adrians Walk Management (Number 2) Company Ltd | Households | 2004 |
| Adrok Properties Limited | Real estate | 2016 |
| Adrx Limited | Health & social care | 2010 |
| ADS 2 Health Limited | Health & social care | 2022 |
| Adsdwood Ltd | Manufacturing | 2026 |
| Advance Motors Limited | Wholesale & retail | 2014 |
| Advance Painting and Decorating Ltd | Construction | 2023 |
| Advanced Care Recruitment Ltd | Health & social care | 2013 |
| Advanced Cleaning Services Limited | Administrative & support | 2013 |
| Advanced Cleaning Technology Ltd | Administrative & support | 1987 |
| Advanced Fabrications Poyle Limited | Manufacturing | 1983 |
| Advanced Protection Services Limited | Administrative & support | 2010 |
| Advanced Surgical Services Ltd | Health & social care | 2025 |
| Advanced Vision Systems Limited | Administrative & support | 2011 |
| Advantage K Properties Ltd | Real estate | 2018 |