| 1 | Mobico Group PLC | Unitedkingdom | Digbeth | National Express House | Birmingham, West Midlands | B5 6DD | nationalexpress.***** | 1992 | $4,325,838,057 | 49,785 | N/A | N/A | N/A |
| 2 | Stagecoach Group LIMITED | Unitedkingdom | Rochallie | 10 Dunkeld Road | Perth and Kinross | PH1 5TW | stagecoach.***** | 1980 | $1,983,337,579 | 24,669 | N/A | N/A | N/A |
| 3 | Grt Bus Group LIMITED | Unitedkingdom | Bridge of Don | 395 King Street | Aberdeen City | AB24 5RP | firstgroup.***** | 1988 | $1,194,972,985 | 20,000 | N/A | N/A | N/A |
| 4 | London General Transport Services LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | goaheadlondon.***** | 1989 | $814,845,707 | 7,742 | N/A | N/A | N/A |
| 5 | Transport For Wales Rail LTD | Unitedkingdom | Pencoed | 3 Llys Cadwyn | Bridgend | CF37 4TH | tfw.***** | 2020 | $777,807,652 | 3,533 | N/A | N/A | N/A |
| 6 | Metroline LIMITED | Unitedkingdom | Mill Hill | Cricklewood Bus Garage | London | NW2 6JP | metroline.***** | 1993 | $437,219,484 | 4,407 | N/A | N/A | N/A |
| 7 | Mtr CORPORATION (crossrail) LIMITED | Unitedkingdom | Moorgate | Fleet Place | London | EC4M 7QS | N/A | 2013 | $420,654,456 | 1,294 | N/A | N/A | N/A |
| 8 | National Express LIMITED | Unitedkingdom | Digbeth | Birmingham Coach Station | Birmingham, West Midlands | B5 6DD | nationalexpress.***** | 1928 | $380,130,928 | 973 | N/A | N/A | N/A |
| 9 | Hs1 LIMITED | Unitedkingdom | London | Kings Place | London | N1 9AG | highspeed1.***** | 1998 | $371,146,599 | 678 | N/A | N/A | N/A |
| 10 | Metroline Travel LIMITED | Unitedkingdom | Mill Hill | Comfortdelgro House | London | NW2 6JP | metroline.***** | 1989 | $350,141,042 | 3,561 | N/A | N/A | N/A |
| 11 | Arriva London North LIMITED | Unitedkingdom | Wood Green | 16 Watsons Road | London | N22 7TZ | arriva.***** | 1988 | $308,091,310 | 4,859 | N/A | N/A | N/A |
| 12 | West Midlands Travel LIMITED | Unitedkingdom | Digbeth | National Express House | Birmingham, West Midlands | B5 6DD | nationalexpress.***** | 1991 | $280,766,209 | 4,609 | N/A | N/A | N/A |
| 13 | East London Bus & Coach Company LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1989 | $265,475,223 | 2,638 | N/A | N/A | N/A |
| 14 | Go South Coast LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | N/A | 2000 | $252,340,766 | 1,924 | N/A | N/A | N/A |
| 15 | Lothian Buses LIMITED | Unitedkingdom | Bellevue | 55 Annandale Street | City of Edinburgh | EH7 4AZ | lothianbuses.***** | 1986 | $250,682,848 | 2,648 | N/A | N/A | N/A |
| 16 | Translink | Unitedkingdom | Glenariffe | Europa Bus Centre | Belfast | BT12 5AH | translink.***** | 2009 | $237,541,090 | 4,000 | N/A | N/A | N/A |
| 17 | London United Busways LIMITED | Unitedkingdom | Shepherd'S Bush | Garrick House, Stamford Brook Bus Garage | London | W4 1SY | londonutd.***** | 1988 | $233,292,746 | 2,652 | N/A | N/A | N/A |
| 18 | Brighton & Hove Bus And Coach Company LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | buses.***** | 1935 | $223,037,079 | 1,393 | N/A | N/A | N/A |
| 19 | Greater Manchester Buses South LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1901 | $199,113,048 | 2,132 | N/A | N/A | N/A |
| 20 | Ulsterbus LIMITED | Unitedkingdom | Sydenham Intake | 3 Milewater Road | Belfast | BT3 9BG | translink.***** | 1966 | $180,416,820 | 2,108 | N/A | N/A | N/A |
| 21 | First West Yorkshire LIMITED | Unitedkingdom | Collingham | Hunslet Park | Leeds, West Yorkshire | LS10 1PL | firstgroup.***** | 1986 | $174,880,958 | 2,012 | N/A | N/A | N/A |
| 22 | Stagecoach Bus Holdings LIMITED | Unitedkingdom | Rochallie | 10 Dunkeld Road | Perth and Kinross | PH1 5TW | stagecoachbus.***** | 1998 | $173,330,796 | 835 | N/A | N/A | N/A |
| 23 | Go North East LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | gonortheast.***** | 1986 | $171,630,360 | 1,719 | N/A | N/A | N/A |
| 24 | Rotala LIMITED | Unitedkingdom | Oldbury | Cross Quays Business Park | Sandwell, West Midlands | B69 3HW | diamondbuses.***** | 2005 | $168,719,344 | 1,515 | N/A | N/A | N/A |
| 25 | Arriva London South LIMITED | Unitedkingdom | Wood Green | 16 Watsons Road | London | N22 7TZ | arriva.***** | 1988 | $161,104,217 | 1,469 | N/A | N/A | N/A |
| 26 | First West Of England LIMITED | Unitedkingdom | Lawrence Hill | Enterprise House | City of Bristol | BS5 0DZ | firstgroup.***** | 1887 | $159,792,497 | 1,576 | N/A | N/A | N/A |
| 27 | South East London & Kent Bus Company LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 1989 | $149,132,385 | 1,388 | N/A | N/A | N/A |
| 28 | First Glasgow (NO.1) LIMITED | Unitedkingdom | Bridge of Don | 395 King Street | Aberdeen City | AB24 5RP | firstgroup.***** | 1986 | $137,414,263 | 1,225 | N/A | N/A | N/A |
| 29 | Scottish Citylink Coaches LIMITED | Unitedkingdom | Glasgow | Killermont Street | Glasgow City | G2 3NW | citylink.***** | 1985 | $120,613,776 | 257 | N/A | N/A | N/A |
| 30 | Transport UK West London Bus LIMITED | Unitedkingdom | Herne Hill | 301,camberwell New Road | London | SE5 0TF | N/A | 2011 | $119,716,510 | 866 | N/A | N/A | N/A |
| 31 | Mcgill's Bus Service LIMITED | Unitedkingdom | Ardgowan | 99 Earnhill Road | Inverclyde | PA16 0EQ | mcgillsbuses.***** | 1949 | $113,724,985 | 1,377 | N/A | N/A | N/A |
| 32 | Fife Scottish Omnibuses LIMITED | Unitedkingdom | Rochallie | 10 Dunkeld Road | Perth and Kinross | PH1 5TW | fifescottish.***** | 1948 | $113,142,317 | 1,276 | N/A | N/A | N/A |
| 33 | Keolis Amey Metrolink LIMITED | Unitedkingdom | Saint Johns Wood | 19-21 Hatton Garden | London | EC1N 8BA | N/A | 2015 | $108,628,287 | 932 | N/A | N/A | N/A |
| 34 | Transdev Blazefield LIMITED | Unitedkingdom | Burton Leonard | Prospect Park | North Yorkshire | HG2 7NY | harrogatebus.***** | 1991 | $108,394,973 | 1,381 | N/A | N/A | N/A |
| 35 | Stagecoach (south) LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1919 | $107,773,172 | 1,409 | N/A | N/A | N/A |
| 36 | Plymouth Citybus LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | N/A | 1986 | $104,761,615 | 833 | N/A | N/A | N/A |
| 37 | Lincolnshire Road Car Company LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1928 | $97,732,076 | 1,356 | N/A | N/A | N/A |
| 38 | Hct Group Operations Community Interest Company | Unitedkingdom | Clapton | Ash Grove Depot | London | E8 4RH | hctgroup.***** | 2001 | $91,233,237 | 1,205 | N/A | N/A | N/A |
| 39 | Ribble Motor Services LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 2001 | $91,183,260 | 1,216 | N/A | N/A | N/A |
| 40 | Go North West LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | N/A | 2012 | $90,937,405 | 682 | N/A | N/A | N/A |
| 41 | East Kent Road Car Company,limited | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 1916 | $90,275,141 | 1,277 | N/A | N/A | N/A |
| 42 | Metroline West LIMITED | Unitedkingdom | Mill Hill | Comfortdelgro House | London | NW2 6JP | metroline.***** | 2000 | $89,995,100 | 847 | N/A | N/A | N/A |
| 43 | Midland Red (south) LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 1904 | $89,305,133 | 1,128 | N/A | N/A | N/A |
| 44 | Citybus LIMITED | Unitedkingdom | Sydenham Intake | 3 Milewater Road | Belfast | BT3 9BG | translink.***** | 1973 | $88,081,380 | 920 | N/A | N/A | N/A |
| 45 | Arriva LIMITED | Unitedkingdom | East Herrington | 1 Admiral Way | Sunderland, Tyne and Wear | SR3 3XP | arrivabus.***** | 1938 | $87,459,459 | 265 | N/A | N/A | N/A |
| 46 | First South Yorkshire LIMITED | Unitedkingdom | Gildingwells | Ceres Building | Rotherham, South Yorkshire | S65 1AP | firstgroup.***** | 1989 | $83,776,555 | 958 | N/A | N/A | N/A |
| 47 | Tramlink Nottingham (holdings) LIMITED | Unitedkingdom | Marylebone | 105 Piccadilly | London | W1J 7NJ | N/A | 2011 | $81,587,339 | 1 | N/A | N/A | N/A |
| 48 | Busways Travel Services LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1901 | $81,031,017 | 1,120 | N/A | N/A | N/A |
| 49 | Stagecoach Devon LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1919 | $79,661,891 | 1,144 | N/A | N/A | N/A |
| 50 | The City Of Oxford Motor Services LIMITED | Unitedkingdom | Newcastle Upon Tyne | 55 Degrees North | Newcastle Upon Tyne, Tyne and Wear | NE1 6BL | oxfordbus.***** | 1906 | $77,308,884 | 627 | N/A | N/A | N/A |
| 51 | The Yorkshire Traction Company LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1986 | $77,047,417 | 1,068 | N/A | N/A | N/A |
| 52 | Western Buses LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 1913 | $75,371,375 | 938 | N/A | N/A | N/A |
| 53 | Nottingham City Transport LIMITED | Unitedkingdom | Nottingham | 5 South Parade | Nottingham | NG1 2JS | nctx.***** | 1986 | $75,221,478 | 1,068 | N/A | N/A | N/A |
| 54 | Greater Manchester Travelcards LIMITED | Unitedkingdom | Cheetham Hill | Stagecoach Manchester | Manchester, Greater Manchester | M8 8UT | N/A | 1994 | $73,726,964 | 11 | N/A | N/A | N/A |
| 55 | Reading Transport LIMITED | Unitedkingdom | Reading | Kiosk B | Reading | RG1 7QE | N/A | 1986 | $73,648,773 | 661 | N/A | N/A | N/A |
| 56 | Arriva Kent Thameside LIMITED | Unitedkingdom | Maidstone | Invicta House | Kent | ME15 6TX | arriva.***** | 1986 | $71,048,041 | 906 | N/A | N/A | N/A |
| 57 | Cambus LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1931 | $70,386,192 | 789 | N/A | N/A | N/A |
| 58 | Cheltenham And Gloucester Omnibus Company LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 1901 | $67,071,998 | 853 | N/A | N/A | N/A |
| 59 | Arriva The Shires LIMITED | Unitedkingdom | Sundon Park | 487 Dunstable Road | Luton | LU4 8DS | arriva.***** | 1987 | $64,933,031 | 892 | N/A | N/A | N/A |
| 60 | Arriva Yorkshire LIMITED | Unitedkingdom | East Herrington | 1 Admiral Way | Sunderland, Tyne and Wear | SR3 3XP | arrivabus.***** | 1904 | $64,311,060 | 841 | N/A | N/A | N/A |
| 61 | Specialist Passenger Solutions LIMITED | Unitedkingdom | Bridgwater | J24 Huntworth Business Park Hinkley Point C Park and Ride | Somerset | TA6 6TS | N/A | 2015 | $61,171,995 | 518 | N/A | N/A | N/A |
| 62 | Ctrl (UK) LIMITED | Unitedkingdom | Saint Johns Wood | Railtrack Ho | London | NW1 2EE | N/A | 1998 | $59,748,648 | 1,000 | N/A | N/A | N/A |
| 63 | Thames Transit LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1987 | $59,493,812 | 554 | N/A | N/A | N/A |
| 64 | First Glasgow (NO.2) LIMITED | Unitedkingdom | Southside Central | 100 Cathcart Road | Glasgow City | G42 7BH | firstglasgow.***** | 1990 | $58,502,210 | 564 | N/A | N/A | N/A |
| 65 | Diamond Bus (north West) LIMITED | Unitedkingdom | Smithills | Weston Street | Manchester, Greater Manchester | BL3 2AW | diamondbuses.***** | 1995 | $56,609,313 | 493 | N/A | N/A | N/A |
| 66 | Arriva Durham County LIMITED | Unitedkingdom | East Herrington | 1 Admiral Way | Sunderland, Tyne and Wear | SR3 3XP | N/A | 1989 | $56,139,432 | 732 | N/A | N/A | N/A |
| 67 | Diamond Bus LIMITED | Unitedkingdom | Oldbury | Cross Quays Business Park Hallbridge Way | Sandwell, West Midlands | B69 3HW | diamondbuses.***** | 1990 | $55,096,034 | 504 | N/A | N/A | N/A |
| 68 | Translink | Unitedkingdom | Belfast | 47 East Bridge Street | Belfast | BT1 3NR | translink.***** | 2002 | $55,015,399 | 997 | N/A | N/A | N/A |
| 69 | Centrebus LIMITED | Unitedkingdom | Braunstone Town | 43 Wenlock Way | Leicester | LE4 9HU | centrebus.***** | 1999 | $53,214,203 | 645 | N/A | N/A | N/A |
| 70 | Arriva North West LIMITED | Unitedkingdom | Formby | 73 Ormskirk Road | Sefton, Merseyside | L9 5AE | arrivabus.***** | 1953 | $52,901,194 | 760 | N/A | N/A | N/A |
| 71 | Centrewest LIMITED | Unitedkingdom | London | Macmillan Ho | London | W2 1TY | N/A | 1993 | $50,902,601 | 1,400 | N/A | N/A | N/A |
| 72 | Red & White Services LIMITED | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | stagecoachbus.***** | 1937 | $49,585,334 | 790 | N/A | N/A | N/A |
| 73 | Arriva Midlands LIMITED | Unitedkingdom | East Herrington | 1 Admiral Way | Sunderland, Tyne and Wear | SR3 3XP | arrivabus.***** | 1987 | $48,908,863 | 721 | N/A | N/A | N/A |
| 74 | First Cymru Buses LIMITED | Unitedkingdom | Felindre | Heol Gwyrosydd | Swansea | SA5 7BN | firstcymru.***** | 1914 | $48,115,805 | 733 | N/A | N/A | N/A |
| 75 | First South West LIMITED | Unitedkingdom | Camborne | Union Street | Cornwall | TR14 8HF | firstbus.***** | 1929 | $47,056,098 | 675 | N/A | N/A | N/A |
| 76 | First Hampshire & Dorset LIMITED | Unitedkingdom | Fareham | Gosport Road | Hampshire | PO16 0ST | firstgroup.***** | 1985 | $45,227,309 | 534 | N/A | N/A | N/A |
| 77 | First Manchester LIMITED | Unitedkingdom | Paddington | 8th Floor | London | W2 1AF | N/A | 1993 | $44,935,413 | 428 | N/A | N/A | N/A |
| 78 | First Bus Central Services LIMITED | Unitedkingdom | Paddington | 8th Floor the Point | London | W2 1AF | N/A | 2009 | $44,469,649 | 508 | N/A | N/A | N/A |
| 79 | Nst Transport Services LIMITED | Unitedkingdom | Little Singleton | Discovery House | Lancashire | FY4 5RU | nstgroup.***** | 1995 | $44,115,325 | 2 | N/A | N/A | N/A |
| 80 | London Transit LIMITED | Unitedkingdom | Shepherd'S Bush | Garrick House | London | W4 1SY | ratpdevtransitlondon.***** | 2021 | $43,317,356 | 541 | N/A | N/A | N/A |
| 81 | Bluebird Buses LIMITED | Unitedkingdom | Rochallie | 10 Dunkeld Road | Perth and Kinross | PH1 5TW | stagecoachbus.***** | 1918 | $42,610,877 | 579 | N/A | N/A | N/A |
| 82 | Proximo LIMITED | Unitedkingdom | Chester | 1 Park House | Cheshire West and Chester | CH1 4QN | proximo.***** | 2002 | $42,198,544 | 381 | N/A | N/A | N/A |
| 83 | Zeelo LIMITED | Unitedkingdom | Kegworth | Cooper Parry Wealth | Leicestershire | DE74 2SA | zeelo.***** | 2016 | $42,108,838 | 128 | N/A | N/A | N/A |
| 84 | Nottingham Trams LIMITED | Unitedkingdom | Finsbury | Milton Gate | London | EC1Y 4AG | thetram.***** | 2011 | $40,331,949 | 315 | N/A | N/A | N/A |
| 85 | Arriva Kent & Surrey LIMITED | Unitedkingdom | Maidstone | Invicta House | Kent | ME15 6TX | arriva.***** | 1908 | $40,062,914 | 548 | N/A | N/A | N/A |
| 86 | London Buses LIMITED | Unitedkingdom | City of London | 5 Endeavour Square | London | E20 1JN | N/A | 1985 | $39,268,833 | 592 | N/A | N/A | N/A |
| 87 | First Aberdeen LIMITED | Unitedkingdom | Bridge of Don | 395 King Street | Aberdeen City | AB24 5RP | kingcoaches.***** | 1986 | $38,069,523 | 512 | N/A | N/A | N/A |
| 88 | East London Bus LTD. | Unitedkingdom | Stockport | One Stockport Exchange | Manchester, Greater Manchester | SK1 3SW | N/A | 2008 | $36,722,626 | 325 | N/A | N/A | N/A |
| 89 | Cardiff City Transport Services LIMITED | Unitedkingdom | Llanedeyrn | Sloper Road | Cardiff | CF11 8TB | cardiffbus.***** | 1986 | $36,091,995 | 550 | N/A | N/A | N/A |
| 90 | Strathclyde Partnership For Transport | Unitedkingdom | Glasgow | 131 St Vincent Street | Glasgow City | G2 5JF | spt.***** | 1980 | $35,849,189 | 600 | N/A | N/A | N/A |
| 91 | Trent Motor Traction Company Limited(the) | Unitedkingdom | Heanor | Mansfield Road | Derbyshire | DE75 7BG | trentbarton.***** | 1913 | $35,145,728 | 685 | N/A | N/A | N/A |
| 92 | Arriva Northumbria LIMITED | Unitedkingdom | East Herrington | 1 Admiral Way | Sunderland, Tyne and Wear | SR3 3XP | N/A | 1986 | $33,828,246 | 672 | N/A | N/A | N/A |
| 93 | Arriva Cymru LIMITED | Unitedkingdom | East Herrington | 1 Admiral Way | Sunderland, Tyne and Wear | SR3 3XP | arriva.***** | 1930 | $33,373,297 | 478 | N/A | N/A | N/A |
| 94 | Highland Country Buses LIMITED | Unitedkingdom | Rochallie | 10 Dunkeld Road | Perth and Kinross | PH1 5TW | N/A | 1995 | $32,336,120 | 544 | N/A | N/A | N/A |
| 95 | Bluestar | Unitedkingdom | Southampton | Empress Road | Southampton | SO14 0JW | solentblueline.***** | 2014 | $30,024,935 | 500 | N/A | N/A | N/A |
| 96 | T F L Surface Transport | Unitedkingdom | Eltham | 14 Pier Walk | London | SE10 0ES | tfl.***** | 2017 | $29,874,325 | 500 | N/A | N/A | N/A |
| 97 | Reading Buses LIMITED | Unitedkingdom | Reading | Great Knollys Street | Reading | RG1 7HH | reading-buses.***** | 1985 | $29,874,325 | 500 | N/A | N/A | N/A |
| 98 | Tolworth Bus Garage | Unitedkingdom | New Malden | Kingston Road | London | KT5 9NU | londonutd.***** | 2019 | $29,528,413 | 500 | N/A | N/A | N/A |
| 99 | First Group | Unitedkingdom | Collingham | Henconner Lane, Bramley | Leeds, West Yorkshire | LS13 4LD | firstgroup.***** | 2011 | $29,528,413 | 500 | N/A | N/A | N/A |
| 100 | Tram Operations LIMITED | Unitedkingdom | Beddington | Coomber Way | London | CR0 4TQ | tramway.***** | 1995 | $29,247,932 | 248 | N/A | N/A | N/A |