Is it permissible to take a sum of money in exchange for returning merchandise whose value has not yet been paid?

If the sale is concluded and binding, it is not permissible to annul it except by mutual consent. This is called iqālah (cancellation by mutual consent), and it is recommended. The preponderant opinion is that iqālah is permissible for more or less than the original price, and this is what I lean towards. If the price increases, it becomes a new sale, not a cancellation, so there is no harm in you taking an increase over the price, because in contracts, what matters are the meanings, not the wordings, and because the suspicion of usury is negated. As for the prohibited bay’ al-’inah ( ’inah sale), it is selling a commodity for a deferred price then buying it back for a lower price.