The club announced that a disciplinary panel had found the player guilty of five breaches of contract relating to his behaviour on the substitutes' bench during last month's Champions League defeat at Bayern Munich.
The 27-year-old has also been given a written warning as to his future conduct and suspended for two weeks, although the latter punishment is deemed to have already been served.
Chief among those contractual breaches was the conclusion Tevez had not fulfilled "an obligation to participate in any matches in which the player is selected to play for the club when directed by a club official".
He was also found not to have carried out "lawful instructions of any authorised official of the club".
Tevez was accused by manager Roberto Mancini of refusing to play as a substitute during the second half of the 2-0 loss at the Allianz Arena on September 27.
The Italian added the Argentinian would be "finished" at the club as a result but Tevez denied the allegations, blaming a misunderstanding.
He insisted he had merely refused to warm up, something he deemed unnecessary as he had already done so.
Tevez was suspended for two weeks while the matter was investigated and asked to attend a disciplinary hearing last Friday.
The club now appear to have found that Tevez did refuse to play but the striker has 14 days to decide whether to appeal to City's board of directors.
City's statement tonight read: "Following a detailed investigation and associated hearing, a disciplinary panel has upheld the charge of misconduct.
"Five separate breaches of contract formed the basis of the decision by the panel.
"As a result Carlos Tevez has been fined four weeks' wages and has been suspended for a period of two weeks (deemed to have already been served). He has received a written warning as to his future conduct.
"Carlos Tevez has been informed in writing of the decision of the disciplinary panel, and the club has written to the Professional Footballers' Association for ratification of the fine."
Should Tevez choose to appeal and have another hearing go against him, he would have the right to a second appeal to the Premier League.
That whole process could see the saga run into December.
Tevez was City's top scorer and talisman during their historic FA Cup-winning campaign last season but has been largely out of favour since a second transfer request and a failure to secure a move in the summer.
He had started just twice before being named on the bench for the sixth time this campaign for the controversial game in Munich.
Tevez is theoretically available for selection but he seems highly unlikely to be recalled by Mancini in the present climate.
The striker has been training alone since returning from suspension almost a fortnight ago.
Below is the statement from Manchester City in full:
Manchester City Football Club can confirm that a disciplinary hearing has been concluded in relation to a charge of misconduct by Carlos Tevez.
The charge relates to events during the Champions League match against Bayern Munich on September 27, 2011.
Following a detailed investigation and associated hearing, a disciplinary panel has upheld the charge of misconduct. Five separate breaches of contract formed the basis of the decision by the panel.
As a result Carlos Tevez has been fined four weeks' wages and has been suspended for a period of two weeks (deemed to have already been served). He has received a written warning as to his future conduct.
Carlos Tevez has been informed in writing of the decision of the disciplinary panel, and the club has written to the Professional Footballers Association for ratification of the fine.
The five contractual obligations found by the disciplinary panel to have been breached are:
1. An obligation to participate in any matches in which the player is selected to play for the club when directed by a club official.
2. An obligation to undertake such other duties and to participate in such other activities as are consistent with the performance of the player's duties and as are reasonably required of him.
3. An obligation to comply with and act in accordance with all lawful instructions of any authorised official of the club.
4. An obligation to observe the statutes and regulations of FIFA and UEFA, the FA Rules, the League Rules, the Code of Practice and the Club rules, including but not limited to breach of Rule E3(1) of the FA Rules (obligation on the player at all times to act in the best interests of the game and not act in any manner which is improper or which brings the game into disrepute).
5. An obligation not to knowingly or recklessly do anything or omit to do anything which is likely to bring the club or the game of football into disrepute or cause the player or the club to be in breach of the rules (as defined in the contract) or cause damage to the club.
Carlos Tevez has the right to appeal this decision to the board of the club. Any appeal must be made within 14 days.