| Addcom IT Limited | Farnham | 2008 |
| Addd Ltd | London | 2022 |
| Addded Limited | Altrincham | 2019 |
| Adddynamics UK Limited | London | 2019 |
| Added Bytes Ltd | Brighton | 2012 |
| Added Edge Consulting Limited | Birmingham | 2025 |
| Added Edge Ltd | Birmingham | 2012 |
| Added Matter Ltd | London | 2023 |
| Added Time Club Ltd | Nottingham | 2024 |
| Added Value Learning Limited | Wotton-Under-Edge | 2002 |
| Added Value Logistics Publications Limited | Matlock | 1994 |
| Added Value Logistics Systems Ltd | Blackburn | 1999 |
| Addedlovely Ltd | Chesham | 2014 |
| Addedme Ltd | Brentford | 2022 |
| Addedpixels Limited | Stockport | 2025 |
| Addelstone Ltd | London | 2026 |
| Addemo Press Limited | Newry | 1986 |
| Addendx Ltd | Birmingham | 2026 |
| Addepar UK Ltd. | Basingstoke | 2021 |
| Addept Computer Services Limited | Kent | 1987 |
| Addept Solutions Limited | | 1989 |
| Adder Analytics Limited | Oxford | 2021 |
| Adder Associates Limited | Berks | 1993 |
| Adder Consulting Limited | Brackley | 2022 |
| Adder Cross Ltd | Montrose | 2015 |
| Adder Digital Technology Limited | Brentwood | 1999 |
| Adder International Limited | London | 2016 |
| Adder Services Limited | Lancashire | 2006 |
| Adderley Network Consulting Ltd | Wimborne | 2014 |
| Addesu Ltd | London | 2020 |
| Addexx Solutions Limited | Stanmore | 2007 |
| Addfuel Ltd | Thornton-Cleveleys | 2026 |
| Addhere Technologies Limited | Daresbury | 2021 |
| Addhop Limited | London | 2013 |
| Addibuddy Ltd | Guildford | 2023 |
| Addico Social Ltd | Stanmore | 2013 |
| Addict London Limited | Reading | 2018 |
| Addicted to the Hustle Limited | Kingston Upon Thames | 2020 |
| Addictive Behaviour Limited | Woodford Green | 2012 |
| Addictive Media Limited | Leeds | 2003 |
| Addictive Tracks Limited | Abingdon | 2014 |
| Addie App Ltd | Prenton | 2022 |
| Addie Soft (UK) Ltd. | London | 2024 |
| Addigram Limited | London | 2024 |
| Addikt Solutions Ltd | Windsor | 2024 |
| ADDIN365 Limited | London | 2015 |
| Addingham IT Ltd | Skipton | 2017 |
| Addingrove Ltd | Slough | 2023 |
| Addington Capital Group Ltd | London | 2024 |
| Addington Consulting Ltd | Reading | 2018 |
| Addington Films Limited | London | 2017 |
| Addis Cloud Technologies Ltd | London | 2021 |
| Addisbrothers Limited | Hednesford, Cannock | 2005 |
| Addison Alfred Ltd | Cardiff | 2021 |
| Addison Anne UK Holdings Limited | Exeter | 2019 |
| Addison Communications Ltd | London | 2015 |
| Addison Consolidated Enterprises Limited | Bury St. Edmunds | 2021 |
| Addison Publications Ltd | | 2002 |
| Addison Software Limited | Liverpool | 2021 |
| Addison VEX Ltd | Southampton | 2015 |
| Addit.Ai Ltd | London | 2025 |
| Addition Communications Ltd | Maidenhead | 2013 |
| Addition Consulting Service PVT Ltd | London | 2024 |
| Addition Financial Limited | London | 2016 |
| Additional Cash Limited | London | 2017 |
| Additional Curates Society | Birmingham | 1932 |
| Additional Intelligence Ltd | Morden | 2026 |
| Additionality Limited | Dartford | 1999 |
| Additiv Ltd | London | 2024 |
| Additive Catchments Ltd | Barnstaple | 2023 |
| Additive Companion Ltd. | London | 2022 |
| Additive Manufacturing Technologies Ltd | Sheffield | 2015 |
| Additive Security Ltd | Pinner | 2019 |
| Additon Limited | London | 2026 |
| Additti Consulting Ltd | London | 2018 |
| Additus Limited | Marlborough | 2024 |
| Addityv Limited | Edinburgh | 2021 |
| Addland Limited | London | 2018 |
| Addleisure Limited | London | 2019 |
| Addlib AI Ltd | London | 2025 |
| Addlife Ltd | London | 2023 |
| Addm Project Management Ltd | Livingston | 2022 |
| Addmaple Ltd | Poole | 2022 |
| Addmonte Ltd | Derby | 2013 |
| Addmore Entertainment Ltd | Camberwell | 2000 |
| Addmsoft Consultancy Ltd | London | 2018 |
| Addmustard Ltd. | Richmond | 2012 |
| Addomedia Limited | Cambridge | 2003 |
| Addon Factory Limited | St. Austell | 2019 |
| Addon Technology Ltd | London | 2001 |
| Addonise Ltd | London | 2026 |
| Addons IQ Limited | Ammanford | 2026 |
| Addooco Fleet Services Limited | Chesterfield | 2026 |
| Addooco IT Limited | Chesterfield | 2008 |
| Addpole Media Ltd | Kington | 2024 |
| Addprofit Ltd | London | 2021 |
| Addr Studio Ltd | Manchester | 2023 |
| Address for Life Ltd | London | 2018 |
| Address Health Limited | London | 2025 |
| Address Intelligence Technologies Limited | London | 2016 |