The news comes after a tribunal ruled that the Bulls had no case to answer over allegations of making an illegal approach to former Wakefield Trinity Wildcats player David Solomona.
Bradford announced the signing of 24-year-old Platt on a two-year contract in October as a replacement for Wigan-bound Michael Withers in the belief that the player had become a free agent following the Tigers’ relegation.
But Castleford argued that as Platt did not have any release clause in his contract he was still a Castleford player, and the Bulls should pay a transfer fee to bring him to Odsal.
The RFL tribunal today ruled in the Tigers’ favour and the two clubs must now enter into negotiations to being the matter to a conclusion.
A Castleford spokesman said: "The Tigers will be speaking to his agent over the next few days to discuss a way forward."