| 20SOMETHING Limited | London | 2019 |
| 20THIRTYONE Ltd | London | 2026 |
| 20TREES Consulting Limited | High Peak | 2015 |
| 20TWENTY Financials Limited | Birmingham | 2016 |
| 20TWENTY Onward Ltd | Didcot | 2019 |
| 20TWENTY People Solutions Ltd | London | 2026 |
| 20X Ltd | Fleet | 2024 |
| 21 and One Ltd | London | 2026 |
| 21 Blackstone Legal Ltd | London | 2025 |
| 21 Brunswick Terrace Hove Limited | Hove | 2007 |
| 21 Buckingham Gate Office Limited | London | 2015 |
| 21 Consulting Limited | London | 2016 |
| 21 Dean Street Limited | London | 1998 |
| 21 Futures Limited | Guildford | 2025 |
| 21 Heene Road Enfield Limited | Enfield | 1999 |
| 21 Hospitality Group Limited | Newcastle Upon Tyne | 1996 |
| 21 Humber Road Limited | London | 2002 |
| 21 Hyde Park Square Freehold Limited | London | 2003 |
| 21 Interiors Ltd | London | 2021 |
| 21 Kent Road Bishopston (Bristol) Management Company Limited | Bristol | 1982 |
| 21 Oaks Limited | London | 2024 |
| 21 Osborne Road Management Company Limited | Southsea | 2004 |
| 21 Prince of Wales Drive Management Company Ltd | London | 1997 |
| 21 Quid Hospitality Ltd | Liverpool | 2023 |
| 21 Racing Ltd | Northampton | 2020 |
| 21 Rockley Road Limited | London | 2001 |
| 21 Royal York Crescent Management Company Limited | Bristol | 1991 |
| 21 Seconds Ltd | Bedford | 2026 |
| 21 SIX Holdings Limited | Curdridge | 2014 |
| 21 Somerset Consulting Ltd | Wellington | 2026 |
| 21 Squared Ltd | London | 2026 |
| 21 Summerfield (Management) Limited | Oxford | 2020 |
| 21 Techinvest Limited | Northwood | 2014 |
| 21&CO Ltd | Manchester | 2019 |
| 21, Home Park Tenants Management Company Limited | Plymouth | 1984 |
| 21/21A Thirsk Road Management Company Limited | Heathfield | 1998 |
| 21/22 Cornwallis Gardens RTM Company Limited | St. Leonards-On-Sea | 2019 |
| 2100 Ventures Ltd | London | 2022 |
| 2102 Commodities Ltd | London | 2013 |
| 2103 Consulting Services Limited | London | 2025 |
| 21052019 Holdings Limited | West Malling | 2019 |
| 2106 Consults Ltd | Bishop'S Stortford | 2020 |
| 211 Film Limited | Ipswich | 2021 |
| 211 Taxis Ltd | Edinburgh | 2020 |
| 2110 Consult Limited | Harpenden | 2009 |
| 2112 Group Limited | London | 2025 |
| 2112 Ltd | Watford | 2023 |
| 2112MARKETING Limited | Northampton | 2005 |
| 2119 Ltd | Hartlepool | 2021 |
| 212 Accounting Ltd | Baxenden | 2020 |
| 212 Degrees Ltd | Whalley | 2009 |
| 212 Engineering Limited | Canvey Island | 2020 |
| 212 Radio Limited | Backwell | 2019 |
| 212 Services Limited | Wigan | 2022 |
| 2123 Tavern ST Ipswich (Freeholdco) Limited | Shirebrook | 2020 |
| 2124 Ltd | Leeds | 2025 |
| 213 New Cross Road Management Company Limited | | 1991 |
| 2131 Ltd. | Sheffield | 2014 |
| 214 Agency Ltd | London | 2023 |
| 215 Domestic Extensions Ltd | Nottinghamshire | 2022 |
| 216 Architecture Ltd | Waltham Cross | 2020 |
| 216 Sussex Gardens Limited | | 1964 |
| 219 Consultancy Limited | Dunstable | 2022 |
| 219 HQ Limited | Coventry | 2025 |
| 219 Iffley Road Residents' Association Limited | Oxford | 1997 |
| 219 Tufnell Park Road Management Company Limited | London | 2008 |
| 21A Architecture Ltd | Newtownards | 2024 |
| 21C Consultancy Limited | London | 2005 |
| 21C Developments Limited | Chichester | 2005 |
| 21C Innovation Partnerships Ltd | London | 2015 |
| 21CB Services Ltd | Manchester | 2014 |
| 21CHG Limited | Winchmore Hill | 2023 |
| 21CTS Ltd | Carmarthen | 2020 |
| 21D Management Limited | Birchwood | 2022 |
| 21DAYS Ltd | Bedworth | 2018 |
| 21ELEVEN Design Studio Ltd | Bradford | 2024 |
| 21J Stress Solutions Limited | Ayr | 2014 |
| 21K Consultancy Ltd | Rainhill | 2012 |
| 21POINT5GROUP Ltd | London | 2024 |
| 21ST Architecture Ltd | St. Albans | 2011 |
| 21ST Army Group Solutions Ltd | Stockport | 2025 |
| 21ST Century Accounting Limited | Margate | 2019 |
| 21ST Century Brands Ltd | London | 2010 |
| 21ST Century Business Ltd | Manchester | 2005 |
| 21ST Century Eco Properties Limited | Slough | 2011 |
| 21ST Century Engineering Limited | | 2007 |
| 21ST Century Geoscience Ltd | High Wycombe | 2019 |
| 21ST Century Investments Limited | Shrewsbury | 2006 |
| 21ST Century Law Limited | Newark | 2012 |
| 21ST Century Ltd | Bedfordshire | 1993 |
| 21ST Century Medical Clinic Limited | Wokingham | 2012 |
| 21ST Century Mindset Limited | Weymouth | 2015 |
| 21ST Century Music Practice Research Centre C.I.C. | London | 2026 |
| 21ST Century Project Design Limited | Surrey | 1997 |
| 21ST Century Software Limited | Norfolk | 1983 |
| 21ST Century Stamps Limited | Eastleigh | 1986 |
| 21ST Century Structural Services Limited | Lytham St. Annes | 2022 |
| 21ST Century Studios Limited | Dorchester | 1997 |
| 21ST Century Tints Limited | Poole | 2005 |
| 21ST Century Wills and Trusts Ltd | Blackpool | 2021 |