The 30-year-old from Nuneaton, ranked number 88 in the world, is now not allowed to play or be involved in any capacity in any Darts Regulation Authority (DRA) sanctioned event until 12 November.
The ban has been backdated to start from 12 March, from when he was initially suspended by the DRA.
The incident occurred on 9 March when Smith-Neale lost a match at an amateur event, the Nuneaton Darts Open at the Lucky Break Sports & Pool Bar in Nuneaton.
The DRA statement said: “The case relates to allegations of assault and threatening behaviour by Smith-Neale.
“After Smith-Neale lost the match, his opponent offered his hand and Smith-Neale punched him in the face. The incident was captured on CCTV and attracted considerable media attention. Smith-Neale was suspended by the DRA pending a hearing.
“At the hearing Smith-Neale accepted the charges against him and claimed that he had felt threatened by his opponent which was why he punched him. This was not fully accepted by the committee.”
The DRA said that he can appeal against the decision.
Smith-Neale regained his Professional Darts Corporation tour card in 2023. He was ranked number 82 at the time of the incident – but has now dropped to 88.