What is the difference between 'assumption' and 'subject to' in mortgage transactions?

Two distinct ways a buyer can take property with existing mortgage debt. Assumption: the buyer formally assumes the loan with the lender's approval. The buyer becomes personally liable; the seller is typically released from liability through a 'novation.' Lender qualifies the buyer (income, credit). The buyer takes title with the loan now in their name. Common with VA, FHA, and USDA loans (which are often assumable); rare with conventional loans (which usually have due-on-sale clauses prohibiting assumption). Subject To: the buyer takes title and makes payments on the existing mortgage, but the loan remains in the seller's name. No lender approval is sought (or obtained). Seller remains primarily liable to the lender. Buyer has no formal relationship with the lender. Risk for seller: if buyer stops paying, seller's credit is damaged and lender will pursue seller. Risk for buyer: due-on-sale clause may trigger if discovered, forcing immediate repayment. Risk for lender: their underwriting is circumvented. Subject to is legal but legally and ethically risky — most professionals avoid it. Assumption is preferable when available because all parties have clear legal positions.