| A Cloud Guru Ltd | Fareham | 2015 |
| A Colbeck Consultancy Ltd | Poole | 2017 |
| A Collective of Foxes Ltd | Camberley | 2025 |
| A Communications Ltd | Manchester | 2005 |
| A Completely Individual Design Ltd | Hertfordshire | 2008 |
| A Connected Home Limited | Norwich | 2015 |
| A Consilio Ltd | Hexham | 2016 |
| A Control Limited | Shanklin | 2000 |
| A Creative Agency Limited | London | 2015 |
| A Creative Direction Limited | Liverpool | 2004 |
| A Cross Production Ltd | Northampton | 2016 |
| A Curious Fact Limited | Bishop'S Stortford | 2023 |
| A Curious Mind Ltd | Slough | 2025 |
| A Curious Tale Limited | London | 2026 |
| A D a Performance Analytics Limited | London | 2013 |
| A D Control Solutions Limited | Brighouse | 2007 |
| A D Maclean Services Limited | Blackpool | 2020 |
| A D Raine Consulting Ltd | Cardiff | 2025 |
| A D Robotics Limited | Warrington | 2011 |
| A D S Print Incorporated Ltd | Church Stretton | 2014 |
| A D T Systems Limited | Bristol | 1993 |
| A D Tyne Ltd | Birmingham | 2016 |
| A D'Souza Ltd | Bury St. Edmunds | 2006 |
| A Damen Consulting Ltd | London | 2025 |
| A Darker Light Limited | London | 2015 |
| A Data Curious Limited | London | 2019 |
| A Davies Computing Ltd | Swindon | 2010 |
| A Day Long Limited | Colchester | 2025 |
| A Day Today Limited | Ruislip, | 2021 |
| A Dhar AG Ltd | London | 2022 |
| A Different Blue Ltd | Wokingham, Berkshire | 2014 |
| A Digital Health Innovation LAB Ltd | Coventry | 2021 |
| A Digital Limited | Kendal | 2009 |
| A Digital Tomato Limited | Reigate | 2022 |
| A Diverse Agency Ltd | London | 2021 |
| A Dog's Dream Limited | Bromsgrove | 2024 |
| A Door Left Ajar Ltd | London | 2026 |
| A Dope Point of View Limited | London | 2020 |
| A DOT Design Limited | Worcester Park | 2007 |
| A Dream Across the Ocean Ltd | Croydon | 2025 |
| A Dream Car Ltd | Long Eaton | 2024 |
| A Dream IT Solutions Ltd | Dartford | 2019 |
| A Drop of Clarity Ltd | London | 2023 |
| A E Controls Limited | Burgess Hill | 2007 |
| A E Dales Consulting Ltd | Bodmin | 2025 |
| A E M Associates Luton Limited | Aylesbury | 1938 |
| A E Print Services Limited | West Wickham | 2014 |
| A E Wedding Photography Ltd | Birmingham | 2007 |
| A Entertainment Ltd | Chadwell Heath | 2024 |
| A Exclamation Ltd | London | 2022 |
| A F J Consulting Ltd | High Wycombe | 2009 |
| A F Nitura Limited | Coventry | 2023 |
| A F Rigging Services Ltd | Epsom | 2014 |
| A Family Affair Films Ltd | Sheffield | 2018 |
| A Feast on Sorrow Ltd | Glasgow | 2023 |
| A Ferster Ltd | Bury | 2014 |
| A FEW Good Productions Ltd | London | 2019 |
| A FEW Good Things Limited | Liverpool | 2022 |
| A FEW Miles South Ltd | Wallingford | 2023 |
| A FEW People Ltd | Swansea | 2023 |
| A FEW Quid Ltd | London | 2025 |
| A FEW Words Press Ltd | London | 2014 |
| A Fierce Storm Limited | Glasgow | 2023 |
| A Film by Biggz Ltd | Enfield | 2021 |
| A Film by GUY Limited | Harrogate | 2014 |
| A Fine Hour Limited | Watford | 2018 |
| A Flock Ascending Limited | Hove | 2018 |
| A Flying Alligator Ltd | Cardiff | 2025 |
| A Flying History Limited | Gillingham | 2011 |
| A for Animation Limited | Bristol | 2024 |
| A for Authors Agency Limited | Harrow | 2019 |
| A Foreign Country Limited | London | 2013 |
| A Found Sound Limited | London | 2012 |
| A Four Exponents Limited | Colchester | 2024 |
| A Fowler Services Limited | Warrington | 2017 |
| A FOX Consultants for Business Limited | Sutton Coldfield | 2009 |
| A FOX on a Box Limited | Bristol | 2013 |
| A French Consultancy Limited | Wimborne | 2025 |
| A Fricker Consultancy Limited | Warrington | 2016 |
| A Fruity Affair Limited | Belfast | 2024 |
| A Fuller Life AI Ltd | London | 2026 |
| A Future Without Limited | Ashwicke | 2007 |
| A G Cribb Consultancy Ltd | London | 2013 |
| A G Feaver Ltd | Sandbach | 2024 |
| A G S Communications & Services Ltd | Ferryhill | 2018 |
| A G Scenery Ltd | Slough | 2011 |
| A G Scenic Services Ltd | St Albans | 2014 |
| A G Smith Consultancy Limited | Knutsford | 2007 |
| A G T V Limited | Wolverhampton | 2003 |
| A G Visual Limited | Uxbridge | 2026 |
| A Game of Two Halves Ltd | Grays | 2019 |
| A Gaming Limited | Hastings | 2026 |
| A Geezer & a Blonde Productions London Limited | London | 2012 |
| A Genius Visuals Ltd | London | 2024 |
| A Ghanbari Ltd | Abingdon | 2026 |
| A Gill Creative Co Ltd | Slough | 2019 |
| A Girls Diary Limited | Gloucester | 2025 |
| A Glittering Stone Limited | Staines Upon Thames | 2023 |
| A Gold Resourcing Limited | Birmingham | 2025 |
| A Good Film Limited | London | 2017 |