What is the ruling on money paid as compensation for a car accident, when it resulted from the fraud of the perpetrator and another person claiming to be the one responsible?

If you know that the money paid to you was taken fraudulently from the insurance company, you must return it to the insurance company because their money is sacrosanct and it is unlawful to take it fraudulently. As for the person who caused the accident, you can either forgive him or agree with him on a compensation that the traffic authorities would have obligated him to pay. You can arrange for him to pay the amount in installments or postpone it. If he refuses, you have the right to file a complaint against him in the Sharia courts. We advise you to thank Allah for your safety and to gently sue the perpetrator or forgive him.