| Orisel Limited | Lincoln | A rating |
| Orison Services Limited T/A Orison Soft and TonerTown | Leeds | A rating |
| Orison Solicitors LLP | Leeds | A rating |
| ORISSA PREMIER DINING LTD | Derby | A rating |
| Orisys UK Ltd | London | A rating |
| Oritain UK Limited | London | A rating |
| Orix Accountants Ltd | Newcastle upon Tyne | A rating |
| ORIX Corporation UK Limited | London | A rating |
| Orkney Crab | Stromness | A rating |
| Orkney Islands Council | Kirkwall | A rating |
| Orlando Refrigeration & Air Conditioning Ltd | Hemel Hempstead | A rating |
| Orleans Park School | Twickenham | A rating |
| Orlen LNG Trading Limited | London | A rating |
| Orley Farm School Trust | Harrow-on-the-Hill | A rating |
| ORLIGHT LIMITED | St Albans | A rating |
| Orluna LED Technologies Limited | Dunstable | A rating |
| ORLYN LTD T/A Vasantha Vilas | London | A rating |
| ORM Systems UK Ltd | Stanmore | A rating |
| ORMAZABAL UK LIMITED | St. Helens | A rating |
| Orme View Care Home Limited | Llandudno | A rating |
| Ormiston Academies Trust | Birmingham | A rating |
| Ormiston Park Academy | Aveley | A rating |
| Ormiston Rivers Academy | Burnham-on-Crouch | A rating |
| Ormiston Sandwell Community Academy | Oldbury | A rating |
| Ormiston Victory Academy | Norwich | A rating |
| Ormonde Advisory Limited | London | A rating |
| ORMONDE HOUSE CAPITAL LTD | LONDON | A rating |
| ORMOS TRADES LTD | WATFORD | A rating |
| Orms Designers + Architects Ltd | London | A rating |
| Ormskirk Cricket Club | Ormskirk | A rating |
| Ormskirk Mini-Mart Ltd | Ormskirk | A rating |
| ORMSKIRK ROAD PETROL STATION LIMITED | SKELMERSDALE | A rating |
| Ornami Imports Limited | Long Eaton | A rating |
| ORNAMORE UK LTD | LONDON | A rating |
| Ornate I Limited | London | A rating |
| Ornate Rugs Ltd | London | A rating |
| Orno Limited | Birmingham | A rating |
| ORNUA FOODS UK LIMITED | Leek | A rating |
| Oromah International Ltd | Bristol | A rating |
| Orona Ltd | Sunbury-on-Thames | A rating |
| Orphalan UK Limited | London | A rating |
| Orphans in Need | Bradford | A rating |
| ORPHEO LIMITED | London | A rating |
| Orpheus Technology Limited | London | A rating |
| ORPHEX TECH LIMITED | Marlow | A rating |
| Orpington Cafe Ltd | Orpington | A rating |
| Orpington Pharmacy | Orpington | A rating |
| Orpington Specsavers Hearcare Ltd | Orpington | A rating |
| orpiva | London | A rating |
| Orrell Grange Nursing Home | Bootle | A rating |
| Orrell Park Hotel | Liverpool | A rating |
| Orrell Red Triangle Cricket Club | Wigan | A rating |
| Orri UK Ltd | London | A rating |
| ORRICK HERRINGTON & SUTCLIFFE (UK) LLP | LONDON | A rating |
| ORS Consulting (UK) Limited | Aberdeen | A rating |
| ORSA PROJECTS LIMITED | London | A rating |
| Orsett & Thurrock Cricket Club | Thurrock | A rating |
| Orsett Communications Ltd T/A Real Thai Massage | Grays | A rating |
| Orsett House Retirement Home Limited | Stoke-on-Trent | A rating |
| ORSIS (UK) LIMITED | HARROGATE | A rating |
| Orsted Power (UK) Limited | London | A rating |
| ORT UK | London | A rating |
| Orta Tech Ltd | Salford Quays | A rating |
| Ortae Ltd | Birmingham | A rating |
| Ortak Limited | Orkney | A rating |
| ORTAKSLAR LTD | Hoddesdon | A rating |
| ORTEC FINANCE LTD | LONDON | A rating |
| Ortec UK Ltd | Birmingham | A rating |
| ORTEGA LTD | Waltham Abbey | A rating |
| Ortel Ltd | Gloucester | A rating |
| ORTENZ & CO LIMITED | LONDON | A rating |
| Orthene Chemicals Limited | Harrow | A rating |
| Ortho-Clinical Diagnostics | Pencoed,Bridgend | A rating |
| Orthobio Therapeutics UK Limited | Cambridge | A rating |
| ORTHODOC MEDICS LTD | Manchester | A rating |
| Orthodontic Care Limited | Brentford | A rating |
| Orthodontic Gallery | Ilford | A rating |
| ORTHOHOUSE SOLUTIONS LTD | London | A rating |
| Orthomobility Ltd | Abingdon | A rating |
| Orthonika Limited | London | A rating |
| ORTHOREMEDYCLINIC(ORC) LTD | Stockport | A rating |
| Orthosmile Earls Court Ltd | London | A rating |
| Orthoson Limited | Oxford | A rating |
| Orthowise UK LTD | London | A rating |
| ORTO BEDFORD STREET LTD | Belfast | A rating |
| Ortus Technology Ltd | Sudbury | A rating |
| Ortus Telematics Ltd | Sudbury | A rating |
| Oru Space Ltd. | London | A rating |
| Oruna Finest Cuisine Ltd | Market Drayton | A rating |
| Orveda Ltd | London | A rating |
| Orveon Global Ltd | London | A rating |
| Orvio Ltd | London | A rating |
| Orwell Management Services Ltd T/A A1 Clutches | Tipton | A rating |
| Orwell Mencap | Ipswich | A rating |
| Orwell Multi Academy Trust | IPSWICH | A rating |
| Orwell Offshore ltd | Ipswich | A rating |
| Orwell Park School | Ipswich | A rating |
| Oryon Imaging and Healthcare Ltd | London | A rating |
| Oryx Align Limited | London | A rating |
| Oryx Facilities Management Limited | London | A rating |
| Oryx Re Limited | London | A rating |
| OS Builders Merchants Ltd | London | A rating |
| OS Comms Limited | Suffolk | A rating |
| OS Designs and Partners Limited | London | A rating |
| OS Glasgow Limited | Glasgow | A rating |
| OS Retail LTD | London | A rating |
| OS SOLUTIONS LTD | BOLTON | A rating |
| OSA Systems ltd | Witney | A rating |
| Osaava Limited | Bromley | A rating |
| OSAGYEFO ENTERPRISES LTD | London | A rating |
| OSAKA (HIGH WYCOMBE) LIMITED | High Wycombe | A rating |
| Osaka (Reading) Limited | Droitwich | A rating |
| Osaka Autotraders Limited | Manchester | A rating |
| Osaka Gas UK, Ltd | London | A rating |
| OSAS AFRICAN FOODS SUNDERLAND LTD | Sunderland | A rating |
| Osbon Medicals Limited | Edgware | A rating |
| Osborn Associates Ltd | Edenbridge | A rating |
| Osborne & Little Ltd | London | A rating |
| Osborne Clarke Services | Bristol | A rating |
| Osborne Co-Operative Academy Trust | Stanford-le-Hope | A rating |
| Osborne Partners Limited | London | A rating |
| Osborne Street Surgery Limited | Grimsby | A rating |
| OSBORNE TRAINING CENTRE LIMITED T/A OSBORNE TRAINING CENTRE | Watford | A rating |
| Osbornes Solicitors | London | A rating |
| OSBOURNE PINNER LIMITED | London | A rating |
| Oscar Acoustics | West Kingsdown | A rating |
| Oscar Apparels Ltd | Essex | A rating |
| Oscar Chauffeur Ltd | Edgware | A rating |
| Oscar Humphrey Group Limited | London | A rating |
| Oscar Products Limited | Acton | A rating |
| OSCAR'S FISH AND CHIPS LIMITED | Coulsdon | A rating |
| Oscar& Bentleys Ltd | Canterbury | A rating |
| OSCARS PIZZA CO LTD | KINGS LANGLEY | A rating |
| Oscarshamm Polo Team | Liphook | A rating |
| OSCIS LTD | Huddersfield | A rating |
| Oscore Limited | Suffolk | A rating |
| OSE CONSULTING LTD | NOTTINGHAM | A rating |
| OSF DIGITAL UK LTD | London | A rating |
| OSG UK Limited | Basildon | A rating |
| OSG WATER LTD | LONDON | A rating |
| Osh Catering LTD | LONDON | A rating |
| Osha Rani Moss Trading As - The Ceramic Studio | Tonbridge | A rating |
| Oshibi | York | A rating |
| Oshima Shipbuilding Europe Limited | London | A rating |
| Oshino Lamps (UK) Limited | Nottingham | A rating |
| Oshwal Association of the UK | Nothhaw | A rating |
| OSHWAL ASSOCIATION OF THE UK | HERTS | A rating |
| OSI FOOD SOLUTIONS UK LIMITED | SCUNTHORPE | A rating |
| Osiris Concepts Ltd | London | A rating |
| Osiris Resources | Bristol | A rating |
| Osiris Solicitors Ltd | London | A rating |
| Oskad UK Ltd | London | A rating |
| OSL UK PVT Limited | London | A rating |
| OSLAC CONSULTING LTD | WEMBLEY | A rating |
| Osler Diagnostics Ltd | Oxford | A rating |
| Oslond Limited | Southsea | A rating |
| Osm Offshore Aberdeen Limited | Westhill | A rating |
| Osman Consulting Ltd | Solihull | A rating |
| Osmans Dental Practices | COVENTRY | A rating |
| OSMANTHUS CARE LTD | Wellingborough | A rating |
| Osmaston Grange Care Home Ltd | Belper | A rating |
| Osmaston Surgery | Derby | A rating |
| OSME EDUCATION LTD | Bromley | A rating |
| OSMOS SISTEMAS ELECTRICOS UK LTD | London | A rating |
| Osmosis (Holdings) Limited | London | A rating |
| Osmosis ACD Limited | London | A rating |
| Osmosis Buyer Limited (UK) | Dereham | A rating |
| Osmosis Training Ltd | London | A rating |
| Osmosys Software Solutions UK Limited | London, | A rating |
| OSN Development Limited | Hayes | A rating |
| Osome Ltd | London | A rating |
| Osprey Investors (UK) LLP | London | A rating |
| Osprey Investors Limited | London | A rating |
| Osprey Leadership Foundation | Oakham | A rating |
| Osprey Shipping Limited | Portishead | A rating |
| Osprey Stores Ltd | Newport | A rating |
| OSPREYS RUGBY LIMITED | SWANSEA | A rating |
| OSPT Ltd | Oxford | A rating |
| OSR IT SOLUTIONS LTD | Thames Ditton | A rating |
| OSRL (Oil Spill Response Limited) | Southampton | A rating |
| OSS Digital Consulting Limited | Feltham | A rating |
| OSSETT CRICKET CLUB | OSSETT | A rating |
| Ossila Limited | Sheffield | A rating |
| Ossington Investment Ltd | London | A rating |
| OSSO Energy Plc | London | A rating |
| OSTAR SOLUTIONS LTD | London | A rating |
| Ostberg Sinclair & Co Ltd | London | A rating |
| Osteo-Clinic (UK) Ltd | Leighton Buzzard | A rating |
| Osteopathic Consultancy | Camberley | A rating |
| Osteotec Limited | Thatcham | A rating |
| Osteria Dell Angolo Limited | London | A rating |
| Osteria Toscana Ltd | London | A rating |
| Osterley Park Group Ltd | Isleworth | A rating |
| OSTLERS YARD HOLDINGS LTD | Bournemouth | A rating |
| Ostrum Tech Limited | Crawley | A rating |
| Oswestry School | Oswestry | A rating |
| OTA BUILDERS LTD | Birmingham | A rating |
| Otaaki UK Limited | Enfield | A rating |
| Otala.Markets LTD | London | A rating |
| Otang Care Ltd | Erdington | A rating |