| Absn Holdings Limited | Professional & scientific | 2008 |
| Absn Renewables Limited | Real estate | 2008 |
| Absolute AF Limited | Financial services | 2015 |
| Absolute AM Ltd | Financial services | 2019 |
| Absolute Design Associates Limited | Information & communication | 1994 |
| Absolute Fabrications Limited | Manufacturing | 2002 |
| Absolute Financial Services LLP | | 2007 |
| ABT Property (Newark) Limited | Real estate | 2025 |
| AC Construction & Safety Services Ltd | Professional & scientific | 2018 |
| Academy Systems (UK) Ltd. | Manufacturing | 2000 |
| Access Accounts Services Ltd | Professional & scientific | 2002 |
| Accommodations Europe Limited | Real estate | 2019 |
| Accu-Set Healthcare Ltd | Health & social care | 2018 |
| Acer Landscapes Design & Construction Limited | Construction | 2004 |
| ACM Trans 24/7 Ltd | Transport & logistics | 2020 |
| Acorn Clearprint Limited | Manufacturing | 2019 |
| Acorn Legal Limited | Professional & scientific | 2003 |
| Acquire Control Limited | Construction | 2005 |
| Acreage Estates Ltd | Real estate | 2023 |
| Acreholm Limited | Construction | 1975 |
| Action Demolition Limited | Construction | 2005 |
| Active Ideas Ltd | Manufacturing | 2005 |
| Active Integrated Systems Limited | Information & communication | 2019 |
| Active Listening Therapies Limited | Health & social care | 2019 |
| Active Minds KS2 Provision Limited | Education | 2026 |
| Active Newark CIC | Education | 2023 |
| ACTIVE4TODAY Limited | Education | 2015 |
| ACTIVE8 Managed Technologies (London) Ltd | Information & communication | 2014 |
| ACTIVE8 Managed Technologies (Silverstone) Ltd | Administrative & support | 2020 |
| ACTIVE8 Managed Technologies IT Ltd | Information & communication | 2010 |
| ACTIVE8 Managed Technologies Limited | Manufacturing | 2013 |
| Adam Bathrooms Limited | Construction | 2008 |
| Adam FOX Plant Hire & Contractors Limited | Construction | 2019 |
| Adam Grimshaw Limited | Information & communication | 2018 |
| Adams Agility Equipment Ltd | Manufacturing | 2026 |
| Adane Construction Ltd | Construction | 2026 |
| Adaptawave Technology Ltd | Professional & scientific | 2026 |
| Addhomes Ltd | Real estate | 2014 |
| ADH Management Ltd | Professional & scientific | 2020 |
| ADN Accounts & Book Keeping Services Limited | Professional & scientific | 2001 |
| Adotd Consulting Ltd | Arts & recreation | 2024 |
| ADP Installations Limited | Construction | 2017 |
| ADR UK Tyremart Limited | Wholesale & retail | 1978 |
| Adrenalin Jungle Limited | Arts & recreation | 2006 |
| ADS Assets Ltd | Professional & scientific | 2020 |
| Advanced Property Services UK Limited | Construction | 2003 |
| Advanced Software Group Limited | Information & communication | 2017 |
| Adventure Day Vans Limited | Wholesale & retail | 2021 |
| Advertise With US Limited | Professional & scientific | 2016 |
| Aegir Consulting Limited | Professional & scientific | 2011 |
| Aegis Service and Aftercare Ltd | Administrative & support | 2009 |
| Aegis Technologies Limited | Administrative & support | 2003 |
| Aemete Core Support Services Ltd | Administrative & support | 2024 |
| Aems Consulting Limited | Professional & scientific | 2016 |
| Aeratech Limited | Construction | 2006 |
| Aerial Marks Ltd | Professional & scientific | 2025 |
| Aeroacumen Limited | Professional & scientific | 2013 |
| Aesthetic Dental Studio Limited | Health & social care | 2011 |
| Aether Film Productions Ltd | Information & communication | 2021 |
| AF Trucking Services Limited | Transport & logistics | 2024 |
| Affiliate Performance Marketing Limited | Professional & scientific | 2015 |
| Afrodeutsche Ltd | Arts & recreation | 2019 |
| AG Civils Limited | Construction | 2011 |
| Agapply Limited | Extraterritorial | 2017 |
| Agdr Property Limited | Real estate | 2025 |
| Agera Associates Ltd | Professional & scientific | 2019 |
| Agility Vision Shows Ltd | Arts & recreation | 2026 |
| Agjt Property Ltd | Real estate | 2022 |
| AGP Building Supplies Limited | Wholesale & retail | 2020 |
| Agripin Limited | Other services | 2020 |
| AGS Contracts Ltd | Construction | 2025 |
| AGS Controls Ltd | Professional & scientific | 2024 |
| AHF Property Management Limited | Real estate | 2005 |
| Aidas Services Ltd | Construction | 2026 |
| Aidev Limited | Professional & scientific | 2016 |
| Aiir Ltd | Information & communication | 2013 |
| AIM a Little Higher Ltd | Education | 2018 |
| AIM Cars Limited | Wholesale & retail | 2014 |
| Aina London Ltd | Wholesale & retail | 2025 |
| Airquick (Newark) Limited | Wholesale & retail | 1974 |
| Airquick Rail International Limited | Wholesale & retail | 2024 |
| Aitw Limited | Financial services | 2022 |
| AJ Bathrooms & Tiles Ltd | Wholesale & retail | 2019 |
| AJ Services Engineering Limited | Professional & scientific | 2020 |
| Aj's Creative Ltd | Arts & recreation | 2025 |
| Aj's Dance Limited | Administrative & support | 2025 |
| AJR Developments Limited | Construction | 2011 |
| Akansel Kamara Estates & Heritage Company Ltd | Real estate | 2025 |
| AKF Drivers Ltd | Transport & logistics | 2018 |
| AKM Projects Limited | Wholesale & retail | 2022 |
| AKM Repairs Ltd | Manufacturing | 2024 |
| Akoy Limited | Wholesale & retail | 2025 |
| Akvehiclelogistics Ltd | Wholesale & retail | 2021 |
| AL Mulk Fragrances Ltd | Administrative & support | 2025 |
| Al's Perfect Plumbs Limited | Construction | 2018 |
| Alan Rowe Ltd | Construction | 1983 |
| Alarmue Ltd | Manufacturing | 2024 |
| Alexander Green and Partners Ltd | Financial services | 2008 |
| Alexander Mews Management Limited | Households | 2018 |
| ALF Media Ltd | Information & communication | 2013 |