Portadown forfeit match against Ards after playing suspended Robert Garrett
Portadown have forfeited the points they won by beating Ards on Saturday and been fined £350 for playing Robert Garrett while he was suspended.
Midfielder Garrett scored in the 3-1 victory at Shamrock Park but should not have been on the pitch.
Ards have now been handed the win on a 3-0 scoreline and move up to seventh in the league, with the Ports now eight points adrift at the foot of the table.
The matter was discussed by an Irish FA Disciplinary Committee on Wednesday.
According to the IFA website, Garrett was to serve a one-match ban, effective from Monday 24 October, but Portadown say they understood that the suspension was to commence a week later.
A statement released by the IFA on Thursday morning said the sanction had been imposed for a breach of Article 22.1 of the Disciplinary Code "following consideration of Portadown's written comments".
"The Committee was satisfied that Portadown knew or ought to have known the current rules with regard to suspensions," read the statement.
The issue of Garrett's eligibility was raised by Ards prior to the Premiership game between the sides and formally brought to the attention of the IFA by the Northern Ireland Football League.
The result at Shamrock Park was Portadown's fourth win of season, meaning they would have wiped out the 12-point deduction imposed before the start of the season.
They are now on minus-three points.