Benjamin Kidd was seen stepping out of a Toyota Aygo and attacking the victim with a sharp weapon.
The court heard that the man was purchasing drugs from Kidd when he was attacked for "short changing" him.
The victim sustained serious injuries including a severed finger and cuts to his arm, head and back.
His finger was not able to be reattached following the attack at about 8.20pm on May 19, on Burwaye Close, in Lichfield,
Police located the vehicle and searched the adjacent property, where they found Kidd hiding in the loft space behind a water tank.
The 30-year-old, of Birch Avenue, Cannock, pleaded guilty to causing grievous bodily harm and was jailed at Stafford Crown Court on Monday.
Detective Constable Gareth Morris said: “We are pleased with the sentence given.
"This was a violent attack where the victim suffered serious life changing injuries and this behaviour will not be tolerated in Staffordshire.”