Leave him alone for a while. When he comes to you with a fake loan slip, you call the police. Moreover, don't pay Yuan You back the 9000 he really owes, but wait until the court (because the other party may not give you a receipt on the grounds that you owe 20000). The other party is a fraud. You can ask the public security organ for handwriting identification. No matter how similar it is, there are differences. In the face of modern science and technology, criminals will eventually reveal their true colors. As for the sentence of several years, it depends on the case. The amount of 20,000 yuan is a maximum penalty of less than three years.