Yo fella
Its a pain in the ar*s now the new law has come out.
1 goto the post office and ask for a V62 APPLICATION FORM FOR A VEHICLE REGISTRATION CERTIFICATE V5C.
2 fill out the form with all known info.
3 send with a cheque for £19 to dvla address writen on the back and wait 4 weeks for it to return. 2 weeks if you was the registered keeper and are just after a duplicate.
if you want to TAX the vehicle like me today and you dont have the green slip then tough. I have to wait 4 weeks for the registration to arrive and then I can TAX it. SAD....
you used to be able to fill out a V62 and a V10 at the post office and with the MOT Doc and INSURACE Doc you could get TAX that day but not any more. Makes you wonder why people drive round with no TAX.
Hope I have been of help.
Miniman