The Red Bull driver faced a stewards investigation after winning the Singapore race having been suspected of not keeping to within 10 car lengths of the safety car during the final full safety car period.
Perez, who won by 7.595s from Ferrari's Charles Leclerc, was handed a five-second penalty and a reprimand for the incident, keeping the victory.
The stewards offered two different decisions.
For the reprimand, the stewards said they "do not accept that the conditions were such as to make it impossible or dangerous for PER to have maintained the required less than 10 car length gap."
But added that "nevertheless, we took into account the wet conditions and the difficulties highlighted by PER as mitigatory circumstances for this incident."
In the second decision, the stewards said that Perez had ignored a warning from race direction to close the gap, which is why he was handed the five-second penalty.
"Car 11 was the lead car on lap 36 during the second safety car period in the race. It was admitted that while the lights of the safety car were still on, PER failed to keep within 10 car lengths of the safety car between turn 13 and turn 14," the stewards' document read.
"This occurred notwithstanding the fact that the Race Director had issued a warning to the team that PER was not respecting the less than 10 car lengths regulation between turns 9 and 10. The team passed that warning on to PER.
"We refer to Doc 56 by which we imposed a reprimand on PER for a breach of the same regulation during the first safety car deployment during the race. As this was the second breach of Article 55.10 by PER during the race and followed an express warning from the Race Director, we determined to impose a 5-second time penalty on PER."
Perez explained the incident and what he told the stewards during the post-race press conference: "There was a bit of miscommunication.
"On the places where I could keep up with him [the safety car], he was super slow. On the places where I could not keep up with him, he was fast. So it was a bit of miscommunication there.
"But I think these conditions are not normal. It's fully understandable that the conditions that we were in, and we were facing, especially in the final sector, were super tricky. The stewards were pleased with my explanation, and they understood it."
Perez remains third in the F1 drivers' standings, two points behind Leclerc, and 106 points behind championship leader Max Verstappen who missed out on his first chance to seal the world title finishing seventh.
