It was announced on Friday that United were paying 'in excess' of the €10m buyout clause in Amorim's Sporting contract.
And Geraldes is convinced the option should only come into effect over a summer transfer window.
He told O Jogo: "Given that the departure of Ruben Amorim will only be official on the 10th, Sporting is good to announce the new coach only on the 11th.
"However, the contractual details of the exit remain to be clarified, namely the reason why the value of the termination clause is this, especially at a time outside the summer transfer window. At the very least, the clause should apply only to the summer market and not to any other period of the season, something that has not been safeguarded."
Geraldes also stated: "The Sporting project was essentially centered on Ruben Amorim. Thus, the departure of a coach with such autonomy represents a complex challenge for the management of the club. Although it was a choice of the Board, it is evident that, when it came to this point, such a decision would come at a cost.
"Amorim is dear not only internally, but also among fans and players. This impact, of course, is already generating instability. We talk about someone who is a coach with the 'house key' of the club."