The PSL's statement reads: "The members of the PSL DC unanimously agreed that the complainant, Dynamos, convinced the DC that the player in question, who was registered by Bay United under the name and identification document of Realeboga Bolly Matlou, and played for Bay United in National First Division League fixtures, was not Realeboga Bolly Matlou.
"Therefore, Bay United was found guilty of fielding an unregistered player.
"The parties have until Tuesday morning to make submissions on mitigation and aggravation for sanction."
At least four matches could be affected by the decision, and judgement will affect the sides' League status next season.
Dynamos finished second last, and as the situation stands they will be relegated to the Vodacom League. They will hope Bay are docked points to rescue them from relegation.
Bay finished 11th with 35 points, while Dynamos finished on 32 points.