| 123BH Limited | Sandy | 2025 |
| 123CONSULTING Ltd | Harrow | 2015 |
| 123CONTROLS Ltd | Aylesbury | 2025 |
| 123CPB Ltd | London | 2022 |
| 123GPG321 Limited | London | 2018 |
| 123HR Limited | Plymouth | 2012 |
| 123M Property Ltd | Chichester | 2024 |
| 123UK Consulting Limited | Richmond | 2023 |
| 124 Sports Management Ltd | Banbridge | 2020 |
| 1240 Designs Limited | Richmond | 2021 |
| 1244 Taxis Ltd. | Livingston | 2007 |
| 1245 Limited | Liversedge | 2022 |
| 1248 Taxis Ltd. | Edinburgh | 2007 |
| 125 OBS (Nominees 2) Limited | London | 2006 |
| 125 OBS GP Limited | London | 2014 |
| 125 Systems Ltd | Warrington | 2025 |
| 1254 Taxis Ltd. | Edinburgh | 2007 |
| 1255 Limited | Halifax | 2025 |
| 12571538 Limited | Heckmondwike | 2020 |
| 125DB Ltd | Horley | 2015 |
| 126 North Hill (Plymouth) Management Company Limited | Plymouth | 1995 |
| 126 Tanner's Hill Limited | London | 2000 |
| 1260 Edin. Ltd. | | 2003 |
| 1262 Edin. Ltd. | Livingston | 2003 |
| 1266 Music Group Ltd | Glasgow | 2020 |
| 127/133 Strathville Road Limited | | 1996 |
| 1270 Edin Ltd. | Edinburgh | 2004 |
| 1273 Taxis Ltd. | Galashiels | 2007 |
| 1279 Taxis Ltd. | Edinburgh | 2010 |
| 128 Barry Road Limited | London | 2003 |
| 128 Consulting Ltd | Haslemere | 2026 |
| 128 Kennington Park Road Freehold Limited | London | 2021 |
| 1281 Taxis Ltd. | Edinburgh | 2015 |
| 1284 Limited | Leicester | 2020 |
| 1286 Taxis Ltd. | Glasgow | 2010 |
| 1287 Edin Limited | Edinburgh | 2010 |
| 12883242 Ltd | Cardiff | 2020 |
| 129 Kilburn Lane Limited | London | 1997 |
| 129 Marlborough Road Management Company Limited | London | 2003 |
| 129 North Limited | Nottingham | 2014 |
| 1292 Taxis Ltd. | Dunfermline | 2010 |
| 12930264 Ltd | Southampton | 2020 |
| 1295 Taxis Ltd. | Duns | 2018 |
| 1296 Taxis Ltd. | Penicuik | 2019 |
| 1299 Taxis Limited | Edinburgh | 2016 |
| 129GROUP Ltd | North Shields | 2021 |
| 12:00-TEN Limited | Leeds | 2019 |
| 12:01 Group Ltd | London | 2026 |
| 12:51 Consulting Ltd | Hove | 2022 |
| 12AM Media Ltd | London | 2022 |
| 12AP Limited | Leeds | 2023 |
| 12B Solicitors Limited | London | 2019 |
| 12BOXES Limited | London | 2002 |
| 12CW Limited | Farnborough | 2026 |
| 12GP Management Limited | London | 2014 |
| 12MT Social Ltd | Uckfield | 2021 |
| 12NK Management Limited | Leicester | 2025 |
| 12SIGMA Ltd | London | 2020 |
| 12TH Design Co Ltd | Bridgwater | 2024 |
| 12TH Floor Studio Ltd | London | 2021 |
| 12TH MAN Interim Solutions Ltd | Droitwich | 2010 |
| 12TH MAN Media Ltd. | Glasgow | 2011 |
| 12TH MAN Productions Ltd | Bolton | 2024 |
| 12TH Studio Ltd | Lancing | 2022 |
| 12TH Works Ltd | London | 2025 |
| 12TREES Consulting Services Ltd | Banbury | 2022 |
| 13 - 18 Trojan CT Freehold Limited | London | 2023 |
| 13 Architect Ltd | Glasgow | 2019 |
| 13 Architectural Consultants Ltd | Leicester | 2016 |
| 13 Articles Ltd | Eltham | 2023 |
| 13 Blue Commercial Services Ltd | Basildon | 2023 |
| 13 Bronsart Road Management Company Limited | | 2002 |
| 13 Brunswick Square (Gloucester) Limited | Gloucester | 1982 |
| 13 Church Crescent Freehold Limited | Ware | 2009 |
| 13 Consulting Ltd | Bromley | 2022 |
| 13 Degree Limited | Bury St. Edmunds | 2023 |
| 13 Design Limited | Edinburgh | 2014 |
| 13 Devonshire Buildings Limited | Avon | 1989 |
| 13 ENG Limited | Hexham | 2018 |
| 13 Hampton Road Limited | Middlesex | 1987 |
| 13 Kensington Place Bath (Management) Limited | Bath | 1981 |
| 13 Mari Limited | Glasgow | 2024 |
| 13 Marine Square (Brighton) Limited | Brighton | 1992 |
| 13 Marlborough Road Limited | London | 2010 |
| 13 Medical Communications Ltd | Whitstable | 2018 |
| 13 Princes Street Management Company Limited | Etchingham | 2007 |
| 13 Salisbury Road (Hove) Limited | Hove | 2003 |
| 13 SH Limited | London | 2025 |
| 13 Solutions Ltd | Northampton | 2021 |
| 13 Stars Ltd | High Wycombe | 2022 |
| 13 Things Ltd | London | 2014 |
| 13 Thirteen Design Ltd | Aviemore | 2016 |
| 13 Thornfield Road Management Company Limited | | 1998 |
| 13 Victoria Walk Management Limited | Bristol | 1987 |
| 13-15 Gentleman's ROW (Enfield) Management Co. Ltd. | Enfield | 1994 |
| 13-36 Colehill Gardens (Freehold) Limited | Chichester | 2007 |
| 13.10 Studio Ltd. | London | 2024 |
| 13/6 Ltd | Edinburgh | 2013 |
| 130 Atelier Limited | Blackpool | 2020 |
| 130 Eglington Road Management Company Limited | London | 1999 |