Due-on-sale clause is a form of acceleration clause found in some mortgages, especially savings and loan mortgages, requiring the mortgagor to pay off the mortgage debt when the property is sold, resulting in automatic maturity of the note at the lender’s option.  This clause effectively eliminates the possibility of the new buyer’s assuming the mortgage unless the mortgagee permits the assumption, in which case the mortgagee might increase the interest rate or charge an assumption fee.