Shiels was handed a two-match ban by a Scottish Football Association fast track tribunal for making comments that impinged upon the character of Dallas and for not acting in the best interests of football.
The decision also sparked an additional two-match punishment, which was suspended from his previous Hampden hearing last month.
The SFA charge stated that the offending comments were his allegations that Dallas had "fabricated" evidence for and during a previous judicial panel hearing and his claim that the official had acted in a "manipulative and devious'" manner.
Shiels had hit out after escaping further punishment for being sent to the stand in a Rugby Park defeat by St Johnstone on November 24, on the advice of Dallas.
The Northern Irishman faced a hearing last month where he was originally accused of misconduct by dissent, adopting an aggressive attitude and by the use of offensive, insulting or abusive language.
The panel upheld the complaint, but only in respect to dissent, and decreed no further punishment was necessary.
Speaking to BBC Scotland the day after the December 13 hearing, Shiels said: "I brought in evidence to disprove the fourth official, who fabricated stuff to try and incriminate me. I don't like that.
"I'm not going to lie down to these people.
"The fabrication was outrageous - at least four different things that were said about me - but he wasn't aware I had visual evidence on my laptop.'"
Dallas, the son of former World Cup referee and former head of the SFA's referees department Hugh Dallas, had said he was "extremely surprised and disappointed" by the allegations.
The Kilmarnock manager served a three-game touchline ban last month for other comments made regarding match officials, with his suspended two-game ban stemming from that hearing.