Charles Leclerc kept his third-placed finish at the Abu Dhabi Grand Prix but Ferrari were fined €50,000 for "an inaccurate fuel declaration" for the 22-year-old's SF90.
Stewards highlighted a discrepancy in the car ahead of Sunday's race, although the investigation was delayed until after the event.
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Leclerc subsequently finished third, behind Formula One champion Lewis Hamilton and Red Bull's Max Verstappen.
The FIA then discovered there had been a difference of 4.88 kilograms between what Ferrari declared and what it had measured for Leclerc's car.
It was deemed Ferrari had breached the rules but only the team were sanctioned, with Leclerc remaining in P3.
