Many lenders will require their position be stated these days. In the old days, the first to file made it the senior mortgage. However, when people started getting piggy back loans where they buy a house with two loans, one for 80% and the other for 20%, the documents clearly states that the 80% is the senior loan even if the junior loan file first. With all the refinancing over the years, new lenders might require that and old lender agrees to subordinate their loan. This is why buying foreclosures at auction can be so tricky. You need to have a detailed title search done and all of the document read to find out what agreements were made.