| 1ST Active Ltd | Southampton | 2010 |
| 1ST Advisory Ltd | Poole | 2020 |
| 1ST AID Door Repair Company Limited | London | 1998 |
| 1ST Architects (Scotland) Ltd | Inverkeithing | 2019 |
| 1ST Awards Limited | Knutsford | 2019 |
| 1ST Business Rescue Ltd | Preston | 2019 |
| 1ST Call Accounts Ltd | Aldershot | 2012 |
| 1ST Call Company Formations Limited | Bristol | 1998 |
| 1ST Call Electrical Ltd | Sheffield | 2021 |
| 1ST Call Limited | Walsall | 2025 |
| 1ST Call Plumbers Ltd | London | 2026 |
| 1ST Call Solutions Ltd | Cardiff | 2019 |
| 1ST Call Training Limited | Poole | 2010 |
| 1ST Call UK Financial Services Ltd | Nottingham | 2024 |
| 1ST Capital Holdings Ltd | Sale | 2020 |
| 1ST Capital Partners Ltd | London | 2025 |
| 1ST Central Advisory Ltd | London | 2024 |
| 1ST Central Law Limited | Colchester | 2011 |
| 1ST Choice Accountants Ltd | Birmingham | 2016 |
| 1ST Choice Bookkeeping and Payroll Solutions Limited | Rugby | 2023 |
| 1ST Choice Bookkeeping Ltd | Ormskirk | 2026 |
| 1ST Choice Card Payments Ltd | Nottingham | 2022 |
| 1ST Choice Consultancy Ltd | Birmingham | 2020 |
| 1ST Choice Floor Care Ltd | Waterlooville | 1996 |
| 1ST Choice Health and Safety Ltd | Litherland | 2009 |
| 1ST Choice Incorporations Ltd | Cambourne | 2019 |
| 1ST Choice Lighting and Electrical Limited | London | 2009 |
| 1ST Choice Rail Labour Limited | Kent | 2002 |
| 1ST Choice Safety Training Ltd | Leicester | 2014 |
| 1ST Choice Sunshine Care Limited | Plymouth | 2002 |
| 1ST Choice Surveying Services Ltd | Rayleigh | 2018 |
| 1ST Choice Waste & Metals Limited | Stockport | 2005 |
| 1ST Circle Ltd | Brighton | 2026 |
| 1ST City Engineering Consultancy Limited | Retford | 2014 |
| 1ST City Ltd | London | 2010 |
| 1ST Class Consultants Limited | Dagenham | 2024 |
| 1ST Class Energy Limited | St. Albans | 2009 |
| 1ST Class Enterprises Limited | Goole | 2011 |
| 1ST Class Images Limited | Moreton In Marsh | 2017 |
| 1ST Class Research Limited | Horncastle | 2023 |
| 1ST Click Ltd | Horsham | 2023 |
| 1ST Cloud Accountants Limited | Sunderland | 2011 |
| 1ST Concept Designs Limited | Essex | 2001 |
| 1ST Connect Networks Limited | Cambridge | 2000 |
| 1ST Consultants Limited | Westcott Dorking | 1999 |
| 1ST Containers (UK) EOT Trustees Limited | Rainham | 2023 |
| 1ST Corporate Secretary Ltd | Poole | 2020 |
| 1ST Corporation Ltd | London | 2003 |
| 1ST Day Limited | Moffat | 2018 |
| 1ST Direct Drainage Services Limited | Glasgow | 2002 |
| 1ST Direct Maintenance Services Limited | Glasgow | 2002 |
| 1ST Energy UK Ltd | Liverpool | 2020 |
| 1ST Engineering Services Limited | Wolverhampton | 2025 |
| 1ST Financial Consultancy Ltd | Reading | 2015 |
| 1ST Fire Safety Limited | Tenbury Wells | 2014 |
| 1ST for Accounting Ltd | London | 2022 |
| 1ST for Bookkeeping Ltd | Penarth | 2022 |
| 1ST for Comfort Limited | Rochdale | 2007 |
| 1ST for Property Ltd | London | 2004 |
| 1ST Growth Consulting Ltd | London | 2013 |
| 1ST Harmonic Ltd | Hull | 2020 |
| 1ST Heritage Consultancy Ltd | London | 2024 |
| 1ST Horizon Surveying & Engineering Limited | Barnsley | 2006 |
| 1ST Idea Limited | Kingston Upon Thames | 2014 |
| 1ST Identity Check Ltd | Aberdeen | 2026 |
| 1ST Identity Ltd | Wallington | 2019 |
| 1ST Impression Creative Ltd | Barnet | 2014 |
| 1ST Impressions Photography Ltd | Milton Keynes | 2015 |
| 1ST Inspection Service Aberdeen Ltd | Aberdeen | 2025 |
| 1ST K & T Tyres Ltd | Manchester | 2003 |
| 1ST LAB Limited | Birmingham | 2010 |
| 1ST Law & Finance Ltd | Harrow | 2015 |
| 1ST Legal Limited | Ayr | 2012 |
| 1ST Life Consultancy Group Limited | Cardiff | 2020 |
| 1ST Life Group Limited | Penarth | 2024 |
| 1ST Line Consulting Ltd | London | 2010 |
| 1ST Line Defence HSF Limited | Hoddesdon | 2014 |
| 1ST Line Legal Services Ltd | Ammanford | 2020 |
| 1ST Line Ltd | Weymouth | 2008 |
| 1ST Line Services Ltd | Port Talbot | 2023 |
| 1ST Objective Limited | Gerrards Cross | 2009 |
| 1ST Online Solutions Limited | London | 2009 |
| 1ST Option Coin Ltd | London | 2020 |
| 1ST Option Representation Limited | London | 2000 |
| 1ST Pass Services Ltd | Edinburgh | 2020 |
| 1ST PAY Limited | Liverpool | 2023 |
| 1ST Pension Services Limited | London | 2025 |
| 1ST Place Surveying Limited | Market Rasen | 2016 |
| 1ST Planner Ltd | Matlock | 2011 |
| 1ST Planning Limited | Romford | 2018 |
| 1ST Principles Limited | Coventry | 2015 |
| 1ST Protection Solutions Ltd | Birmingham | 2024 |
| 1ST Regulatory Ltd | Marlow | 2009 |
| 1ST Resource Ltd | Leeds | 2006 |
| 1ST Response Legal Ltd | Manchester | 2026 |
| 1ST Risk Solutions Limited | Tunbridge Wells | 2016 |
| 1ST Route Limited | London | 2012 |
| 1ST Safety Solutions Limited | Perth | 2011 |
| 1ST Solution Consultancy Ltd | London | 2024 |
| 1ST Solution Consulting Ltd. | Reading | 2015 |