The Midlands club are 22nd in the Championship, one point from safety in the relegation zone and facing a drop to League One - the third tier of English football - unless they can find form in their final five games of the season.
Leicester astounded the football world by winning the Premier League against the odds a decade ago, but were relegated last season. They were docked six points earlier this year for breaches of strict English Football League profitability and sustainability rules governing spending.
"An independent Commission’s decision to recommend a six-point deduction on Leicester City Football Club this season has been upheld by an independent Appeal Board," the Premier League, which initiated the original investigation, said in a statement.
Leicester accepted the ruling.
"With the matter now at an end and five games of the season remaining, everyone at the Club is fully focused on the matches in front of us and on shaping the outcome of our season through our results on the pitch," the club said.
Leicester host Swansea City on Saturday.