Callan was riding Ballet Blanc, a 50-1 chance, for Amanda Perrett in the Unibet 3 Uniboosts A Day Handicap.
With two winners on the card already under his belt, Callan took up the running three furlongs into the contest and proceeded to ride a finish but did not apparently realise his error until the rest of the field caught him up after Ballet Blanc had been eased down.
Ballet Blanc was ultimately beaten 115 and three-quarters of a length by the winner, Blazeon Five. Callan is banned between November 9-12, November 14-19, November 26 and November 28.
Callan recently celebrated his first Group One winner since his return from Hong Kong when teaming up with old ally Kevin Ryan on Fonteyn in the Sun Chariot Stakes.
A British Horseracing Authority stewards report on the incident said: "Neil Callan, the rider of Ballet Blanc, unplaced, had appeared to ride a finish a circuit too soon. After being interviewed and shown recordings of the incident, the rider was suspended for 12 days."
Responding to a video of the incident on social media Callan tweeted: "Yep that was embarrassing!!"