Is the penalty clause resulting from backing out of purchasing a car through Murabaha, when the Shariah conditions have not been met, permissible or forbidden?

It is permissible to hold the purchase orderer liable for actual damages if reneging on the promise to purchase results in harm, and it is not valid to stipulate an absolute percentage for compensation. The compensable damage includes actual financial loss, real loss, and certain lost profit. The penal clause is not enforceable if the breach of contract was due to circumstances beyond control, or if no harm befell the other party. In case of dispute, the assessment is referred to the Sharia judge and experts.