Although he never failed a drugs test, Singh was deemed to have breached golf's rules on doping when he told Sports Illustrated earlier this year he had used deer antler spray.
The spray was found to have contained small extracts of IGF-1, a growth hormone on the World Anti-Doping Agency's list of prohibited substances.
The US PGA Tour imposed a sanction on Singh following his admission but the Fijian appealed, saying he was unaware the spray contained any banned substances.
He was later cleared when WADA informed the US Tour the use of deer antler spray was not prohibited unless a positive test resulted.
"Based on this new information, and given WADA's lead role in interpreting the Prohibited List, the Tour deemed it only fair to no longer treat Mr. Singh's use of deer antler spray as a violation of the Tour's anti-doping program," the US Tour said in a statement .
"Since his initial quote was made public, Mr. Singh has cooperated with the Tour investigation and has been completely forthcoming and honest.
"While there was no reason to believe that Mr. Singh knowingly took a prohibited substance, the US Tour Anti-Doping Program clearly states that players are responsible for use of a prohibited substance regardless of intent."
Singh, 50, was ranked number one in the world on three separate occasions between 2004 and 2005. He also won three Majors: the 2000 Masters and the 1998 and 2004 US PGA Championships.