| Agecroft Legal Services Limited | Manchester | 2019 |
| Agecroft Prison Management Limited | London | 1998 |
| Agecurve Limited | Cambridge | 2015 |
| Aged Pilgrims' Friend Society Trust Limited | | 1964 |
| Ageeliy Ltd | London | 2021 |
| Ageing Plant and Infrastructure Ltd | Brimstage Road | 2022 |
| Agelef Holdings Limited | London | 2013 |
| Ageless Cosmetics Ltd | Brentwood | 2017 |
| Ageless Group Limited | Swindon | 2016 |
| Ageless Health Limited | Winchester | 2012 |
| Agellus Holdings Limited | Bury St. Edmunds | 2015 |
| Agellus Limited | Bury St. Edmunds | 2004 |
| Agellus Projects Limited | Wymondham | 2005 |
| Agem Capital Group Limited | London | 2016 |
| Agem Consulting Ltd | Stanmore | 2024 |
| Agema Limited | Coventry | 1999 |
| Agemer Limited | Kingston Upon Thames | 2015 |
| Agemet Limited | Boston | 1977 |
| Agemica Ltd | London | 2023 |
| Agems Consultancy Ltd | East Molesey | 2024 |
| Agemx Expeditions Group Ltd | London | 2018 |
| Agena Consultancy Limited | London | 2018 |
| Agenais Trustees Limited | Banbury | 2024 |
| Agenccy Consultancy Limited | Milton Keynes | 2023 |
| Agence Twentytwo Ltd | London | 2025 |
| Agencja Cezar FWG Limited | London | 2019 |
| Agenco Ltd | Herts | 2005 |
| Agency & Umbrella Justice Management Ltd | Lincoln | 2025 |
| Agency 11 Limited | Leigh-On-Sea | 2013 |
| Agency 12:12 Ltd | London | 2024 |
| Agency 1710 Ltd | Leigh-On-Sea | 2022 |
| Agency 215 Limited | London | 2010 |
| Agency 42 Limited | Somerset | 2009 |
| Agency 49 Ltd | London | 2022 |
| Agency 5 Ltd | Cobham | 2024 |
| Agency 92 Limited | Bushey Heath | 2018 |
| Agency a Limited | Hertford | 2020 |
| Agency Acquisitions Limited | Barnsley | 1993 |
| Agency Administration Limited | Merseyside | 1959 |
| Agency Alchemy Limited | Leicester | 2022 |
| Agency Assist Limited | Southampton | 2024 |
| Agency Bristol Ltd | Bristol | 2021 |
| Agency Bubble Ltd | London | 2023 |
| Agency Business Limited | Berks | 2006 |
| Agency Care Staff Ltd | Corby | 2021 |
| Agency CFO Ltd | Rossendale | 2019 |
| Agency Consultancy Services Limited | Altrincham | 2020 |
| Agency Consulting Limited | Peterlee | 2018 |
| Agency D Ltd | Edgware | 2010 |
| Agency Deep Ltd | London | 2018 |
| Agency Disrupt Ltd | Halesowen | 2024 |
| Agency Dynamics Ltd | Bournemouth | 2025 |
| Agency Entourage Ltd | London | 2025 |
| Agency Exits Ltd | Okehampton | 2025 |
| Agency FIG Ltd | Langport | 2022 |
| Agency for Change Limited | Southwold | 2013 |
| Agency for International Visits Limited | East Sussex | 2005 |
| Agency Forty Four Limited | London | 2025 |
| Agency Ghost Ltd | Leighton Buzzard | 2019 |
| Agency GMR Limited | Manchester | 2024 |
| Agency Hackers Limited | London | 2017 |
| Agency Insight Limited | Wiltshire | 2003 |
| Agency Kilo Limited | Broadstone | 2010 |
| Agency Marketing Limited | Liverpool | 2022 |
| Agency Nation Limited | Tunbridge Wells | 2023 |
| Agency Network Ltd | Birmingham | 2017 |
| Agency NXD Limited | Castlefield | 2019 |
| Agency of Others Ltd. | Mottram St. Andrew | 2017 |
| Agency One Ltd | Winchester | 2014 |
| Agency One Music Limited | Leigh-On-Sea | 2016 |
| Agency Payroll Limited | Portsmouth | 2023 |
| Agency Payroll Services Limited | Leicester | 2021 |
| Agency People (Consultants) Limited | Watford | 2001 |
| Agency Press Limited | London | 1991 |
| Agency PSI Limited | Sale | 2019 |
| Agency Redefined Ltd | London | 2012 |
| Agency Resource Ltd. | Aberdeen | 2000 |
| Agency Services (Reading) Limited | Fordingbridge | 1988 |
| Agency SIX Ltd | Leicester | 2018 |
| Agency Space UK Limited | London | 2012 |
| Agency Springboard Limited | Leeds | 2023 |
| Agency Stack UK Limited | Worthing | 2021 |
| Agency Studio Ltd | Southsea | 2026 |
| Agency Thirty Seven Limited | Nottingham | 2013 |
| Agency TK London Limited | Bolton | 2017 |
| Agency Training Academy Ltd | Manchester | 2025 |
| Agency Vaughan-Harris Ltd | Battle | 2025 |
| Agency Without Walls Limited | Nottingham | 2019 |
| Agency Xpert Ltd | Chorley | 2025 |
| Agency Zero Ltd | Launceston | 2025 |
| AGENCY34 Ltd | Brentford | 2016 |
| AGENCY41 Ltd | London | 2024 |
| AGENCY53 Limited | Eastbourne | 2017 |
| AGENCY7 Ltd | Leeds | 2024 |
| Agencybc Ltd | London | 2021 |
| Agencyeb Ltd | London | 2024 |
| Agencyforce Limited | Cheddar | 2006 |
| Agencygolf Limited | Stockport | 2026 |
| Agencygrand Ltd | Redditch | 2022 |
| Agencyify Holdings Ltd | Mildenhall | 2023 |