These are couple of documents required when purchasing a used car, many people dont have it, so i just wanted to share the formats and tell, that these are just applications to the ETO, The formats can vary.
1) Receipt (Payment receipt, with a 5rs Stamp to make it official)
2) Transfer Letter (Request to ETO from the seller to transfer in the name of the buyer)
3) Delivery Letter (Can be of 2 types, for buyer or seller both or only the seller),
4) Transfer Deed (On Stamp Paper)
5) Form T.O is also important, but ididnt had it, the person who transfered arranged it.
NOTE: Make sure you take signatures, and fill the name of the buyer and seller where ever required, and make the buyer sign his name or the person on whoose name the car is going to be transfered on all required documents where ever required, This make sure that the car wasnt sold on open letter.
When buying a car on open letter, make sure the letter is dated within one month or not dated at all, the date is valid for one month only. (you have to bear extra if its expired) If its possible get a fresh transfer letter made on ur name from the orignal owner.