| ACT Performance Consultants Limited | Crewe | 2015 |
| ACT Professionals Limited | Northampton | 2025 |
| ACT Quick Ltd | London | 2018 |
| ACT Retail Solutions Ltd | Aylesbury | 2017 |
| ACT Risk Solutions Limited | Widnes | 2025 |
| ACT Safe Global Ltd | Poole | 2026 |
| ACT Safety Ltd | York | 2022 |
| ACT Solicitors Ltd | Norwich | 2011 |
| ACT Studios Limited | Sutton Coldfield | 2015 |
| ACT Sustainability Ltd | Reading | 2018 |
| ACT Sustainably Limited | Tenby | 2005 |
| ACT Sustainably SME Limited | Tenby | 2025 |
| ACT Therapeutics Ltd | Newmarket | 2020 |
| ACT Three Ltd | Bishop'S Stortford | 2010 |
| ACT TIC UK Ltd | Portishead, | 2011 |
| Act&C Limited | Walsall | 1997 |
| Act&T Limited | Surrey | 2006 |
| Act-Ai Limited | Warrington | 2025 |
| Act-Geo Ltd | Aberdeen | 2024 |
| ACT1 Global Ltd | London | 2017 |
| ACT1VE Group Ltd | Dagenham | 2019 |
| ACT3 Consulting Limited | Hoddesdon | 2021 |
| Acta Accounting Limited | Horley | 2024 |
| Acta Advertising Ltd | London | 2022 |
| Acta NON Verba Limited | High Wycombe | 2016 |
| Acta School Limited | London | 2020 |
| Acta Services Ltd | Swindon | 2008 |
| Actaa Consultants Ltd | Ilford | 2016 |
| Actab Ltd | Edinburgh | 2019 |
| Actabilityuk Ltd | Kent | 2021 |
| Actabo Ltd | Abertillery | 2024 |
| Actacc | Sheffield | 2002 |
| Actaea Consultants Limited | Willesden Green | 2017 |
| Actaeon Advisors Ltd | Watford | 2018 |
| Actaeon Limited | Birkenhead | 2018 |
| Actagen Limited | Norwich | 2016 |
| Actaland Limited | Pevensey | 2008 |
| Actanol Service Ltd. | Wakefield | 2004 |
| Actant Consortium Ltd | Birmingham | 2025 |
| Actant Consulting Limited | Chatham | 2011 |
| Actaperts Outsourcing Ltd | London | 2023 |
| Actar Ellis Brown & Co (UK) Limited | Ilford | 2010 |
| Actaros Consultancy Limited | Newbury | 2016 |
| Actarus Services Ltd | 1St Floor | 2011 |
| Actas UK Ltd | Bromsgrove | 2021 |
| Actavis UK Group Limited | Castleford | 2015 |
| Actavistic Limited | Bristol | 2014 |
| Actavo Hire and Sales UK Limited | Oldbury | 2017 |
| Actax (Uk&I) Limited | London | 2020 |
| Actax (UK) Limited | London | 2013 |
| Actax Accounting & Tax Services Ltd | London | 2011 |
| Actax Consultants Ltd | Woking | 2013 |
| Actax Consulting Ltd | Preston | 2013 |
| Actbaron Limited | Colwick Industrial Estate | 1984 |
| Actc Ltd | London | 2024 |
| Actca Limited | Reigate | 2022 |
| Acte in UK Ltd | Watford | 2024 |
| Actea Consultancy Ltd | Solihull | 2026 |
| Actec Electrical Consulting Ltd | Guildford | 2015 |
| Actech Business Solutions Limited | Bournemouth | 2014 |
| Actech Holdings Limited | Guildford | 1995 |
| Acteniq Ltd | Tugby | 2025 |
| Actennoveo International Group Ltd | Cardiff | 2023 |
| Acteon Group Limited | Norwich | 2001 |
| Acteon Group Operations (UK) Limited | Norwich | 2024 |
| Acteon Integrated Solutions Limited | Norwich | 2016 |
| Acteon South American Investments Limited | Norwich | 2006 |
| Actfast Consultancy Limited | Cardiff | 2019 |
| Actforce Limited | Cheshunt | 2003 |
| Actgold Int'L Trading Limited | Cardiff | 2008 |
| Acti Plus Ltd | London | 2018 |
| Acti-Ve Qaqc Consultants Ltd | Leeds | 2023 |
| Actiblast Ltd | Doncaster | 2025 |
| Acticare Limited | Hertford | 2004 |
| Acticore Ltd | Wolverhampton | 2025 |
| Actif Consulting Ltd | Newcastle Upon Tyne | 2021 |
| ACTIF4 Limited | Auchterarder | 2019 |
| Actifhr Limited | Towcester | 2014 |
| Actiframe Limited | St. Andrews | 2021 |
| Actify Limited | Ely | 2001 |
| Actify Solutions Ltd | Bristol | 2014 |
| Actigen Limited | Cambridge | 1997 |
| Actihub Ltd | Birchington | 2022 |
| Actikay Limited | Oxford | 2016 |
| Actilia Limited | Beverley | 2013 |
| Actima Associates Limited | Reigate | 2002 |
| Actimed Limited | Wetherby | 2006 |
| Actimed Therapeutics Ltd | Ascot | 2016 |
| Actimerce Consultancy Limited | Lee-On-The-Solent | 2019 |
| Actimo Limited | Carshalton | 2003 |
| Acting Accountants Limited | Charmouth | 2002 |
| Acting International & Co Ltd | London | 2013 |
| Actinide Limited | London | 2008 |
| Actinista 2016 Limited | Harrogate | 2016 |
| Actinium CS Limited | Reading | 2005 |
| Actinum Limited | Warrington | 2017 |
| Actio Consilium Ltd | London | 2022 |
| Actio Consulting UK Limited | Wellingborough | 2013 |
| Actio Legal Services Limited | Cheltenham | 2010 |
| Actio Pauliana Ltd | Sheffield | 2010 |