rs125

hi..

Ive not long set up a part time business (buying and selling cars)and have just sold my first car
Ive filled out section 10 and gave this part to the buyer (green part)..
Do i have to sign the registered keeper (seller) part (section 8,red part) even though im obviously not the registered keeper.(should i have got the previous owner to sign this when i bought it)

sorry if this seems obvious to alot of people but im new to this and dont want to get things wrong with the first car ive sold..

thanks