In Ming and Qing land sales, a seller could come back after the sale and ask the buyer for more money. The custom was called 找价, “seeking the price,” or 加找. A seller could claim that “the price was not enough.” The historian Cao Shuji found that after the Qianlong era, 加找 became a standard contract form.
A 2012 study in the law journal The Jurist cites the finding that repeated 找价, even after a deed of final sale, was “a very common custom.” Qing law later limited it. Where a deed of final sale did not mention extra payments, none were allowed.