The Saints tried to beat Football League rules by putting their holding company into administration.
A league statement said: “The board concluded that an administrator had been appointed in respect of the club or part of its undertaking or assets.
“Accordingly, it was left with no alternative other than to invoke its ‘Sporting Sanctions’ regulations and apply a 10-point penalty to the club.
“The other provisions of The League’s insolvency policy also become effective.
“As the insolvency event occurred after The Football League’s deadline of the fourth Thursday in March, the points deduction will take effect in the current season, if Southampton avoid relegation to League 1 or next season, if the club does not avoid relegation.”
