This is a ready made legal document which you can print and fill out. When you make a downpayment for a property purchase in Spain you enter into a binding agreement which has penalties should either party not go ahead with the sale. This is one reason why the phenomenon of "gazumping" is not possible in Spain. Once you enter into this agreement either side will lose out if the sale is not completed. The buyer will lose the deposit or the seller will have to pay compensation to the buyer. The document is set out in two columns with Spanish on the left and English on the right.