| ACS Management Group Limited | London | 2022 |
| ACS Midlands Holdings Limited | Longbridge | 2025 |
| ACS Mortgages Limited | Derby | 2017 |
| ACS Payroll Limited | Prestwich | 2024 |
| ACS Private Clients Ltd | Milton Keynes | 2019 |
| ACS Time Critical Services Group Limited | Surbiton | 2024 |
| ACS Venture Group Ltd | Hillsborough | 2025 |
| ACS Ventures Ltd | Cardiff | 2020 |
| Acsa Capital Ltd | Cardiff | 2024 |
| Acsals Limited | Bingley | 2013 |
| Acsel Advisors Limited | Brighton | 2003 |
| Acsmj Dublin Limited | London | 2020 |
| Acsmj Luton Limited | London | 2020 |
| Acsmj South Godstone Limited | London | 2020 |
| Acsn Ltd | Milton Keynes | 2019 |
| Acsons Investments Limited | Cheadle | 2025 |
| Acsquared Holdings Limited | Newton-Le-Willows | 2021 |
| ACT (Holdings) Kent Limited | Maidstone | 2023 |
| ACT Furniture Manufacturers Limited | Birmingham | 1977 |
| ACT Group Holdings Ltd | Leamington Spa | 2024 |
| ACT Health Ltd | London | 2021 |
| ACT Holdings Limited | Birmingham | 2023 |
| ACT Logic Limited | Whitehaven | 2025 |
| ACT OFF Holdings Limited | Hove | 2025 |
| ACT Portfolio Holdings Ltd | Cobham | 2026 |
| ACT Property Solutions Ltd | London | 2025 |
| ACT Sider Limited | London | 1997 |
| ACT Sustainably Group Holdings Limited | Tenby | 2025 |
| ACT Transact Ltd | Birmingham | 2025 |
| ACT Venture Capital (N.I.) Limited | Belfast | 1994 |
| Acta Properties Ltd | London | 2019 |
| Actaea Group Limited | Ware | 2015 |
| Actaprint Holding Company Limited | Harrow | 2023 |
| Actaris Holding Ltd | London | 2014 |
| Actcap Limited | Hitchin | 2020 |
| Actea Holdings Limited | Saltash | 2021 |
| Acteon West Africa Holding Limited | Norwich | 2020 |
| Actesso Holdings Limited | Lee-On-The-Solent | 2018 |
| Actev II Limited | London | 2015 |
| Actev Limited | London | 2013 |
| Acti Consulting Limited | Brighton | 2015 |
| Actia ACP Holdings Limited | London | 2025 |
| Actia Partners Limited | London | 2025 |
| Actic Advisors Limited | Slough | 2009 |
| Actif Group Ltd | Tyldesley | 2019 |
| Actiflex Ltd | London | 2013 |
| Acting Office Investment Limited | London | 2024 |
| Actinium Holdings Ltd | Reading | 2025 |
| Actinoid Group of Companies Ltd | St. Andrews | 2020 |
| Actio Advisors Ltd | Marlborough | 2020 |
| Actio Holdings Ltd | London | 2022 |
| Action 8 Energy Limited | London | 2021 |
| Action 8 Holdings Limited | London | 2020 |
| Action 97 Limited | Stowmarket | 2022 |
| Action BUS Limited | London | 2009 |
| Action Consulting (UK) Ltd | Henlow | 2006 |
| Action Finance Limited | Portsmouth | 2010 |
| Action for Children Pension Trustee Limited | Watford | 1952 |
| Action Global Ltd | London | 2024 |
| Action Holdings Limited | London | 1962 |
| Action Import and Export Group Limited | Southport | 2014 |
| Action International Group EOT Limited | Southport | 2023 |
| Action Telecommunications Solutions Ltd | | 1999 |
| Actioneager Projects Limited | Bedford | 1992 |
| Actionplan Compliance Services Ltd | Gloucester | 2018 |
| Actionzone Holdings Limited | Blackwood | 2024 |
| Actis Fortescue Ventures Limited | London | 2024 |
| Actis Marathon OGH2 Limited | London | 2024 |
| Actium Bidco (UK) Limited | London | 2024 |
| Actium Midco 1 (UK) Limited | London | 2024 |
| Actium Midco 2 (UK) Limited | London | 2024 |
| Actium Midco 3 (UK) Limited | London | 2024 |
| Actium Topco (UK) Limited | London | 2024 |
| Activ'Energy Ltd | London | 2019 |
| ACTIV8 Distribution Holdings Limited | Watford | 2012 |
| Activate Business Finance Limited | Northampton | 2023 |
| Activate Clinical Research Holdings Ltd | Coventry | 2024 |
| Activate Group Holdings Limited | Halifax | 2023 |
| Activate Group Limited | Halifax | 2015 |
| Activate Holdings Ltd | Braintree | 2023 |
| Activate Horizon Ltd | Waterlooville | 2025 |
| Activate INS Limited | Attleborough | 2023 |
| Activate Solutions Group Limited | Gerrards Cross | 2012 |
| Activate Sport and Leisure Ltd | Melksham | 2024 |
| Active Accountancy Limited | Herne Bay | 1995 |
| Active Adult Limited | London | 2020 |
| Active Asset Management (Scotland) Ltd | Livingston | 2013 |
| Active Asset Management Limited | Marlborough | 2014 |
| Active Assets Limited | | 2007 |
| Active Business Finance Limited | London | 2022 |
| Active Business Finance Solutions Limited | London | 2014 |
| Active Business Protection Limited | Guisborough | 2022 |
| Active EMS Owners Ltd | Bury | 2022 |
| Active Estate Planning Limited | Harrow | 2010 |
| Active Estate Planning Solutions Ltd | Edinburgh | 2018 |
| Active Finance Group Ltd | Hove | 2015 |
| Active Finance UK Ltd | Fareham | 2010 |
| Active Financial Advice Ltd | Bristol | 2012 |
| Active Financial Advisers Ltd | Abergavenny | 2019 |
| Active Financial Introductions Ltd | Ashford | 2017 |