Northampton received a £60,000 fine for releasing George North for Wales duty outside the International Rugby Board's designated Test window.
A three-man Premiership Rugby panel made the decision on Wednesday, after the club admitted it had "breached board policy" over player release.
Northampton have already said they will not appeal against the sanction.
The fine relates to Northampton allowed North to play for Wales against Australia on November 30 - which is a date outside the IRB window. Wales lost the game in Cardiff 30-26.
The 12 Aviva Premiership clubs have a solidarity policy over player release for Test matches and the organisation is clearly dissatisfied that the Saints broke ranks.
As part of the Premiership clubs' agreement, only England players are allowed to be released to play for their national side outside of the IRB's international window.
It is believed, however, that when North moved from the Scarlets to Northampton his contract stated that he would be made available for all Wales fixtures.